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RADIUM, 


AND 

OTHER     RADIO-ACTIVE     SUBSTANCES; 

POLONIUM,  ACTINIUM,  AND  THORIUM, 

WITH    A    CONSIDERATION    OF 

PHOSPHORESCENT  AND  FLUORESCENT  SUBSTANCES,   THE 

PROPERTIES  AND  APPLICATIONS  OF  SELENIUM 

AND  THE  TREATMENT  OF  DISEASE  BY 

THE  ULTRA-VIOLET  LIGHT. 

BY 

WILLIAM    J.    HAMMER, 

CONSULTING    ELECTRICAL    ENGINEER. 


NEW  YORK: 
D.  VAN  NOSTRAND  COMPANY. 

LONDON: 
SAMPSON  LOW,  MARSTON  &  COMPANY,  LIMITED, 

St.  Dunstan's  House, 

Fetter  Lane,  Fleet  Street,  E.  C. 

1903. 


COPYRIGHT  1903 
WILLIAM  J.  HAMMER. 


Lftmy 

Wi\J 


CONTENTS. 


FLUORESCENCE. 

What  constitutes  Fluorescence,  Stokes'  Law,  exceptions 
thereto,  Internal  and  surface  dispersion,  Derivation  of  the  word 
fluorescence,  Luminescence,  Fluorescent  liquids,  Fluorescent  paint- 
ings and  writing,  Effect  of  ultra-violet  light,  fluorescent  solids, 
fluorescent  screens,  Willemite,  Prof.  R.  W.  Wood's  ultra-violet 
screen,  The  rhodamin  screen  for  the  mercury  arc » . .  1-3 


PHOSPHORESCENCE. 

Temperatures  of  red-hot  and  white-hot  bodies,  light  without  sensi- 
ble heat  or  flame,  derivation  of  the  word  Phosphorescence,  differ- 
ence between  Phosphorescence  and  Fluorescence,  Bolonese  Phos- 
phorus, Canton's  Phosphorus,  Phosphorescence  by  insolation, 
Ways  by  which  phorescence  may  be  stimulated,  Luminous  Paint, 
effect  of  temperature  variation,  Experiment  with  bust  of  Franklin, 
Phosphorescent  signs,  stars,  philosophical  toy  showing  phases  of 
the  moon,  wand,  postal-cards,  etc.  Prof.  Dewar's  experiments, 
sulphides-of-calcium,  barium,  strontium,  zinc,  etc.,  fluorspar, 
quinia,  fused  boracic  acid,  phosphorescent  ether,  Cathode  rays, 
Atoms  and  corpuscles,  Phosphorescence  in  Crookes'  tubes,  Phos- 
phorescent radiometer,  Edison  tungstate  of  calcium  lamp.  Author's 
reversal  of  the  Roentgen  ray  cycle,  commercial  applications  of  Phos- 
phorescence, stimulation  of  phosphorescence  by  radium  rays, 
Phosphorescence  by  friction  and  electrification,  Phosphorescent 
gases,  Phosphorescent  liquid,  Phosphorescence  by  oxidation  or 
slow  combustion,  Phosphorescent  clouds,  snow,  insects,  fishes, 
etc.,  the  "Pyrophorus  Noctilucus,"  Phosphorescent  flowers, 
plants,  vines,  roots,  fungi,  etc 2-11 

RADIUM,  POLONIUM,  ACTINIUM  AND  THORIUM. 
M.  Henri  Becquerel,  the  founder  of  the  science  of  Radio-activity, 
The  phenomena  of  vacuum  tubes,  experiments  of  M.  Henry  and  M. 
Niewenglowski,  Becquerel 's  remarkable  discovery,  Uranium, 
Pitchblende  (Uraninite),  Polonium  and  its  discovery  by  M.  and 
Mme.  Curie,  Discovery  of  Radium  by  M.  and  Mme.  Curie  and  M. 
Bemont,  Discovery  of  Actinium  by  Debierne,  Crookes'  discovery  of 
Uranium  X,  Radium  in  liquid  air,  Lord  Kelvin's  statement,  Radio- 
active substances,  the  temperature  of  Radium,  M.  and  Mme.  Curie's 
hypothesis,  Radium  a  new  element,  atomic  weight  of  Radium,  the 
standard  of  Radio-activity,  the  cost  of  Radium,  Radium  chloride 
and  bromide,  amount  of  Radium  at  present  in  existence,  test  of  a 


658963 


diamond's  genuineness,  French  and  German  Radium  products, 
enormous  difficulties  met  in  its  preparation,  chemical,  spectro- 
scopic  and  electrical  analysis,  electrometer  method  of  analysis,  the 
Curie  electroscope,  imparted  Radio-activity,  Elster  and  Geitel's 
experiment,  McLennan's  experiment,  stimulation  of  Radio- 
activity, thermo-luminescence  experiments  of  Wiedemann, 
Thompson,  Trowbridge  and  McLennan,  Rutherford's  experiments 
with  Thorium,  Radio-active  gas  from  Radium,  Schmidt's  discovery, 
the  physiological  effects  of  Radium,  Hidden's  theory  regarding  t 
Radio-active  ore,  the  author's  experiment  with  the  "Torpedo  Gal- 
vani,"  Faraday's  and  D'Arsonval's  experiments,  Prof.  Curie's 
experiments  with  guinea  pigs  and  mice,  the  three  types  of 
rays  emanating  from  Radium,  Deviable  "a"  rays,  "a"  rays 
readily  absorbed,  they  constitute  major  portion  of  rays,  "/?"  rays 
in  all  respects  similar  to  cathode  rays,  Tesla's  and  Blondelot's 
claims  as  to  deviation  and  polarization  of  X-rays,  Strutt,  Croolces 
and  Rutherford's  views  as  to  "a"  rays,  "7-"  rays  most  penetra- 
tive, degrees  of  penetration  of  Radium  rays,  effect  of  Magnetism 
on  Radium  rays,  loss  of  strength  of  imparted  Radio-activity,  effect 
of  moisture  and  high  temperature,  non-emanating  and  non-exciting 
character  of  Polonium  and  Uranium,  actual  deposit  of  Radio-active 
matter  by  Radium  and  Thorium,  Newton's  corpuscular  theory  of 
light,  loss  in  weight  of  Radium,  views  of  Profs.  J.  J .  Thomson,  Henri 
Becquerel,  Lord  Kelvin,  Sir  William  Crookes,  P.  Curie  and  A. 
Heydweiller,  coloration  of  glass  by  Radium,  persistence  of  Radium 
rays  versus  Rontgen  rays,  opacity  of  rock  salt  to  Radium  and 
Rontgen  rays,  illustrations  of  penetrating  character  of  Radium  rays 
through  lenses,  lead,  steel,  black  paper,  etc.,  Radiographs  of  mice 
made  with  Radium,  showing  Rontgen  ray  effect,  Radiograph  of  the 
human  hand  made  by  Radium,  photograph  made  by  phosphores- 
cent sulphide  of  calcium,  Radiograph  of  same  objects  made  by 
Radium .  11-42 


THE  PROPERTIES  AND  APPLICATIONS  OF  SELENIUM. 
Variation  of  resistance  of  Selenium  on  exposure  to  light,  discov- 
ery of  Selenium  in  1817  by  Berzelius,  derivation  of  the  word 
Selenium,  characteristics  of  Selenium,  dangerous  character  of 
vapors  of  Selenium,  effects  of  temperature  on  Selenium,  Willoughby 
Smith's  announcement  of  May's  discovery  of  effect  of  light  in  reduc- 
ing resistance  of  Selenium,  early  investigators  into  properties-  of 
Selenium,  Bell's  radiophone,  Prof.  Simon's  discovery  of  speaking 
arc  principle,  Duddell's  speaking  arc,  Ruhmer's  speaking  arc  and 
wireless  telephone  experiments,  theory  of  phenomena  of  speaking 
arc,  Hayes'  radiophone  experiments,  resistance  of  Selenium  cells, 
ratio  of  resistance  in  dark  and  in  the  light,  Shelf ord  Bidwell's  in- 
vention, method  of  constructing  cells,  types  of  cells,  The  Bidwell, 
Ruhmer,  Giltay,  Webb,  Clausen  and  Bronck,  Mercadier  and  Fritts 
cells,  Ruhmer's  latest  type  of  cell,  effects  of  moisture,  Giltay's 
expenments  with  Radiometer,  Ruhmer  and  Giltay  name  telephone 
transmitters  with  Selenium  cells,  author's  experiments  in  firing 


cannon,  lighting  incandescent  lamps,  starting  3  h.p.  motor  and 
generator,  ringing  bells,  operating  horn,  etc.,  by  shielding  a  Selen- 
ium cell  with  the  hand.  Bidwell's  experiments  and  important  state- 
ment. Thermit  and  its  applications,  protection  of  safes  by  Selen- 
ium cells,  Ruhmer's  electrically  controlled  gas  buoy,  Ruhmer's  re- 
markable Photographophone,  employment  of  Photographophone 
as  a  receiver  for  wireless  telephony,  seeing  at  a  distance,  early 
experimenters  in  this  art,  Crookes'  Selenium  and  chromic  acid 
Radiometer,  Prof.  Barnard's  comet  detector,  Ruhmer's  study  of 
eclipse  in  a  fog  with  Selenium  cell,  where  Selenium  is  found,  cost 
of  Selenium,  Saunder's  paper  on  Selenium 42-63 


THE  TREATMENT  OF  DISEASE  BY  ULTRA-VIOLET  RAYS. 

The  Finsen  Institute  at  Copenhagen,  the  deadly  character  of  tu- 
berculosis, Koch's  discovery  of  the  "tubercle  bacillus,"  the  "Blue 
Glass  Craze,"  General  Pleasanton's  book  on  "Blue  and  Sunlight,'* 
the  treatment  of  smallpox,  Finsen's  experiments  with  earthworms 
and  chameleon,  the  treatment  of  Lupus  Vulgaris  by  Ultra- Violet 
light,  the  aluminum  and  iron  electrode  lamps,  use  of  adrenalin  chlor- 
ide for  driving  blood  from  diseased  parts,  use  of  Rontgen  rays  for 
Lupus  treatment,  Dr.  King's  experiment,  the  Finsen  blue  lens  for 
sunlight  treatment,  Finsen's  telescope  tube  for  use  with  carbon  arc, 
opacity  of  blood  to  Ultra- Violet  light,  the  Finsen  pressure  glass, 
method  and  length  of  treatment,  Finsen's  boon  to  humanity,  the 
founding  of  the  Finsen  Institute 63-72 


vii 


LIST  OK  ILLUSTRATIONS. 


FRONTISPIECE:  Showing    Stage    Setting    at    the    time    of    the    author's 
Lecture. 

FIG.   1:  "  Pyrophorus  Noctilucus.  " 

PORTRAIT:  Prof.  Henri  Becquerel. 

FIG.  2:  Radio-active  Substances. 

FIG.  3:  Tubes  of  Polonium  and  Radium. 

FIG.  4:  Apparatus  of  M.  and  Mme.  Curie  for  study  of  Radio- 

activity. 

FIG.  5:  The  Curie  Electroscope. 

FIG.  6:  Radiograph  made  by  Radium  of  Disc,   Rock-salt,  and 

Pitchblende. 

FIG.  7:  Radiograph  of  Lenses  made  by  Radium. 

FIG.  8:  Radiograph  showing  penetration  of  Radium  rays  through 

steel  and  lead. 

FIG.  9:  Radiograph  showing  penetration  of  Radium  rays  through 

double  thickness  of  black  paper. 

FIG.   10:  Radiograph  of  Mouse  made  by  Radium  in  24  hours'  time 

FIG.  11:  Radiograph  of  Mouse  and  Trap  made  by  Radium,  show- 

ing X-ray  characteristics  of  Radium  Rays. 

FIG.  12:  Radiograph  of  Human  Hand  made  by  Radium. 

FIG.   13:  Photograph  of  Various  Metals,  etc.,  made  by  Phosphor- 

escent Sulphide  of  Calcium. 

FIG.  14:  Radiograph  made  by  Radium  of  various  Metals,  etc. 

FIG.   15:  Prof.  Bell's  Radiophone. 

FIG.   16:  Ruhmer's  Apparatus  for  Telephoning  over  a  Beam  of 

Light. 

FIG.  17:  Ruhmer's  Wireless  Telephone  operating  at  night. 

FIG.  IT:  Types  of  Selenium  Cells. 

FIG.  19:  Mercadier's  Cell. 

FIG.  20:  Manometric  Flame  Telephone  and  Selenium  Cell. 

FIG.  21:  Acetylene  Flame  Apparatus.     Selenium  Cell  for  Operat- 

ing Electric  Lamp,  Bell,  Motors,  Cannon,  Horn,  etc. 

FIG.  22:  Three    H.P.    Motor   and    Generator   supplying   bank   of 

Lamps  operated  by  Selenium  Cell,  Relay,  etc. 
Compressed  Gas  Buoy  controlled  by  Selenium  Cell,  etc. 
Diagram  of  Circuits  of  "Selenium"  Buoy  Apparatus. 
Ruhmer's  Photographophone. 
Showing  Interior  of  Ruhmer's  Photographophone. 


FIG.  27:  Mr.  Ernest  Ruhmer  listening  to  his  Photographophone. 

FIG.  28:  Arrangement  of  Circuits  of  Rhumer  Photographophone. 

FIG.  29:  Photograms  used  in  Ruhmer  Photographophone. 

FIG.  30:  Curve  made  with  Selenium  Cell  during  Eclipse. 

PORTRAIT:  Prof.  Niels  R.  Finsen. 

FIG.  31:  Main  Operating  Room,  Finsen  Institute,  Copenhagen. 

FIG.  32:  Showing  Arc  Lamp  and  Finsen  Tubes  in  Operation. 

FIG.  33:  Lupus  Vulgaris  Cured  by  X-rays. 

FIG.  34:  Finsen's  Original  Type  of  Lens  Employing  Sunlight. 

FIG.  35:  Finsen's  Telescope  Tube  for  use  with  Carbon  Arc  Light. 

FIG.  36:  Showing  Arrangement  of  Arc  Lamp  and  Finsen  Tubes. 

FIG.  37:  Finsen  Pressure  Lens. 

FIG.  38:  Showing  Lupus  Vulgaris  Patients  before  and  after  treat- 
ment with  Ultra- Violet  Light. 


A  Lecture  delivered  at  a  meeting  of  the  Amer- 
ican Institute  of  Electrical  Engineers  and 
the  American  Electrochemical  Society,  New 
York,  April  17th,  1903. 


RADIUM  AND  OTHER  RADIOACTIVE  SUBSTANCES 
WITH  A  CONSIDERATION  OF  PHOSPHORESCENT 
AND  FLUORESCENT  SUBSTANCES.  THE  PROP- 
ERTIES AND  APPLICATIONS  OF  SELENIUM  AND 
THE  TREATMENT  OF  DISEASE  BY  THE  ULTRA- 
VIOLET LIGHT. 


BY    WILLIAM    J.     HAMMER. 

The  author  of  this  paper  has  endeavored  to 
exemplify  certain  fundamental  principles  con- 
nected with  the  phenomena  upon  which  he  has 
treated;  and  in  considering  these  subjects,  all  of 
which  may  be  said  to  be  on  the  borderland  of  sci- 
ence, to  bring  out  by  means  of  experiments,  lan- 
tern slides  and  illustrations  which  accompany  the 
paper,  the  practical  and  commercial  side.  He 
entertains  the  hope  that  the  matter  herewith 
submitted  will  prove  of  interest  to  the  members  of 
the  societies  before  whom  he  has  the  honor  of 
appearing,  and  may  serve  in  some  slight  degree 
to  stimulate  investigations  in  these  most  promis- 
ing fields. 

FLUORESCENCE  AND  PHOSPHORESCENCE. 

Sir  George  Stokes  has  given  the  name  of  "Fluorescence"  to 
the  phenomena  which  certain  substances  present  in  altering  the 
very  short  waves  of  ultra-violet  light,  which  are  invisible,  and 
transforming  them  into  waves  of  longer  length  so  that  they 
become  visible  to  our  eyes. 

In  electrical  parlance  a  fluorescent  substance  might  be  termed 
a  step-down  transformer  or  perhaps  more  correctly  a  frequency 
changer  for  light  waves.  Stokes,  as  a  result  of  his  inves- 
tigations, framed  this  law,  "When  the  refrangibility  of 
light  is  changed  by  fluorescence  it  is  always  lowered  and  never, 
raised" — in  other  words,  the  waves  emitted  during  fluorescence 
are  always  longer  than  those  which  are  absorbed,  thus  causing 
fluorescence.  There  are,  in  fact,  cases  where  the  frequency  of 

1 


2  HAMMER:  FLUORESCENCE. 

the  radiations  is  increased;  but  where  there  is  such  an  exception 
to  Stokes'  law  some  sort  of  chemical  reaction  occurs. 

The  lowering  of  the  frequency  of  certain  ultra-violet  radia- 
tions, so  as  to  render  them  visible,  was  known  to  Brewster  in 
1833  and  Herschel  in  1848,  the  former  terming  it  internal  and  the 
latter  surface  dispersion ;  but  it  was  first  explained  and  the  name 
given  to  it  by  Stokes  in  1852,  after  a  form  of  fluorspar. 

In  the  case  of  fluorescence,  the  emission  of  the  light  lasts  only 
so  long  as  the  substance  is  stimulated  by  the  incident  beam ;  but 
in  the  case  of  the  phosphorescence,  the  emission  of  light  con- 
tinues or  persists  after  the  stimulation  has  ceased,  or  the  original 
source  has  been  removed.  The  word  phosphorescence  is  from 
the  Greek  "phosphoros,"  meaning  light  bearer. 

Prof.  E.  Wiedemann  has  suggested  the  name  "luminescence," 
to  cover  fluorescence,  phosphorescence  and  phenomena  of  that 
character  possessed  by  many  substances  whose  light  emissions 
are  unaccompanied  by  flame  or  by  the  temperature  of  ordinary 
light  waves;  but  this  term  can  hardly  be  made  to  cover  the 
Becquerel  rays  emitting  from  radioactive  substances. 

I  have  here  to-night  a  collection  of  tubes  containing  fluorescent 
liquids,  such  as  petroleum,  quinine,  Magdala  red,  cosine,  uranine, 
saffronine,  paviine,  aesculine,  amidophthalic  acid,  fluorescine, 
rhodamin,  etc.,  all  of  which  show  most  beautiful  changes  in 
color  when  viewed  by  direct  and  transmitted  light 

I  also  have  some  of  the  fluorescent  hydrocarbon  "thalleen," 
prepared  by  the  late  Prof.  Henry  Morton,  and  some  of  those  most 
beautiful  fluorescent  substances,  resorcorufin  and  resorcin  blue, 
for  which  I  am  indebted  to  Dr.  Geyer  of  Steven's  Institute. 
Fluorescent  substances  are  particularly  beautiful  in  the  ultra- 
violet light ;  for  instance :  The  yellow  fluorescene  becomes  a  most 
beautiful  green;  the  orange  colored  cosine  becomes  gamboge; 
the  crimson  color  of  Magdala  red  a  bright  scarlet;  the  straw 
colored  sesculine  becomes  a  pale  blue ;  the  transparent  and  color- 
less quinine  gives  its  characteristic  blue  surface  tint ;  the  paraffin 
oil  a  beautiful  blue ;  and  the  various  other  substances  giving  a 
beautiful  surface  color  quite  different  from  that  of  the  interior  of 
the  solution. 

Small  pieces  of  horse-chestnut  bark  or  bark  of  the  ash  tree 
placed  in  a  dilute  ammoniacal  solution  produce  a  most  beautiful 
fluorescent  effect,  as  the  dyeing  material  descends  slowly  through 
the  liquid. 

Flowers  painted  with  these  fluorescent    substances  on  card- 


HAMMER:  PHOSPHORESCENCE.  3 

board  produce  a  most  beautiful  effect  when  light  screened  by 
dark  blue  or  violet  glass  is  thrown  upon  them. 

Sodium  vapor  fluoresces  brilliantly  in  sunlight. 

I  also  have  here  samples  of  tungstate  of  calcium,  platino- 
barium  cyanide,  sulphide  of  zinc,  and  similar  preparations  which 
have  been  extensively  used  in  the  fluorescent  screens  for  X-ray 
work. 

Here  is  a  specimen  of  Willemite  which  when  exposed  to  the 
ultra-violet  light  produced  by  the  bright  snappy  condenser  spark 
between  these  iron  electrodes  shows  a  magnificent  fluorescence. 

Here  is  a  card  with  words  written  with  a  solution  of  platino- 
barium  cyanide  which  fluoresces  beautifully  when  exposed  to 
the  ultra-violet  light  of  the  iron  arc,  especially  when  shielded  by 
the  accompanying  colored  glass  plates. 

I  have  also  one  of  Prof.  R.  W.  Wood's  interesting  ultra-violet 
screens,  consisting  of  four  plates  of  cobalt  glass  between  which 
are  gelatine  films  containing  nitroso-dimethyl-aniline  with  cop- 
per oxide,  which  screen  when  employed  in  front  of  the  arc  lamp 
renders  beautifully  fluorescent  a  lump  of  uranium  nitrate  held  in 
the  focus  of  the  invisible  rays. 

Through  the  courtesy  of  Dr.  Von  Recklinghausen,  I  am 
enabled  to  show  you  a  Cooper-Hewitt  tube  which  is  enclosed  in  a 
screen  soaked  in  rhodamin,  the  best  substance  which  thus  far 
has  been  found  which  is  fluorescent  in  the  light  of  the  mercury  arc. 

It  is  well  known  that  many  bodies  become  red  hot  at  a  tem- 
perature of  between  four  and  five  hundred  degrees  Centigrade, 
and  to  make  them  white  hot  a  temperature  of  between  eight 
hundred  and  a  thousand  degrees  is  necessary;  but  there  are 
many  substances  which  are  phosphorescent  and  which  possess 
the  property  of  giving  off  considerable  light  without  sensible 
heat. 

I  have  here  some  samples  of  two  phosphorescent  substances 
which  have  been  known  for  many  years — one  of  them  a  sulphide 
of  barium  or  Bolonese  phosphorus,  and  the  other  a  sulphide  of 
calcium  or  Canton's  phosphorus.  The  former  was  discovered 
in  1602  by  Casciarlo,  a  shoemaker  in  the  city  of  Bologna  who 
prepared  it  by  the  partial  calcination  of  a  certain  powdered  heavy 
spar  mixed  with  a  little  flour  meal,  which  he  roasted  in  the 
furnace;  and  found  afterwards  that  when  exposed  to  sunlight 
it  would  shine  in  the  dark.  This  preparation  was  succeeded  by 
the  discovery  of  John  Canton,  who  calcined  oyster  shells  with 
charcoal  and  meal  in  a  closed  crucible,  thus  producing  a  brilliant 
phosphorescent  substance  called  after  his  name. 


4  HAMMER:  PHOSPHORESCENCE. 

Phosphorescence  by  insolation — or  exposure  to  sunlight — has 
been  extensively  investigated  by  Prof.  A.  E.  Becquerel  and  Dr. 
John  W.  Draper. 

Practically  all  substances  in  nature  are  phosphorescent,  and 
although  some  of  them  remain  phosphorescent  for  only  one  ten- 
thousandth  of  a  second,  others  retain  their  phosphorescence  for 
hours. 

One  may  expose  sulphide  of  calcium  to  sunlight,  and  after 
placing  it  in  a  dark  room  for  six  weeks  it  will  still  affect  a  photo- 
graph plate. 

Phosphorescence  may  be  stimulated  in  many  ways — by  com- 
bustion, pounding,  rending,  friction,  by  the  vibrations  from 
sources  of  heat,  light  or  electricity;  and  these  various  phosphor- 
escent substances  are  very  susceptible  to  temperature  changes. 

Various  substances  also  phosphoresce  while  undergoing  crys- 
tallization. 

I  have  here  a  large  sheet  of  cardboard  which  has  been  prepared 
for  me  by  Messrs.  Devoe  &  Company,  which  is  covered  with 
seven  coats  of  Balmain's  Luminous  Paint  or  poly-sulphide  of 
calcium,  with  perhaps  a  trace  of  bismuth  and  mixed  with  aerated 
varnish;  and  it  has  been  put  through  hot  calender  rollers.  You 
will  note  that  this  phosphoresces  most  beautifully  when  ex- 
cited by  burning  this  piece  of  magnesium  wire  before  it,  or  by 
focusing  the  arc  light  upon  it.  This  phosphorescence  soon  dies 
out,  however;  but  upon  placing  my  hand  against  the  sheet,  the 
heat  of  my  hand  has  caused  the  card  to  brilliantly  phosphoresce. 
A  cold  object  placed  against  the  cardboard  will  very  much  lessen 
the  phosphorescence  at  that  point. 

When  I  place  this  bust  of  Franklin  between  the  arc  light  and 
the  phosphorescent  cardboard,  you  will  note  I  can  thus  produce 
a  fine  silhouette  of  that  distinguished  philosopher. 

I  have  prepared  for  your  consideration  a  number  of  objects 
coated  with  phosphorescent  substances.  When  I  burn  this 
piece  of  magnesium  wire  in  front  of  this  card,  or  hold  it  before 
the  arc  light,  you  will  note  the  initials  of  the  A.  I.  E.  E.  and  the 
A.  E.  S.,  the  two  societies  before  which  I  have  the  honor  of 
appearing  to-night,  shine  out  brightly.  I  also  have  a  number 
of  incandescent  lamp  bulbs,  coated  internally  and  exter- 
nally with  phosphorescent  substances,  which  you  will  note 
give  considerable  light  when  stimulated  by  the  burning  mag- 
nesium; or  by  turning  on  the  electricity  supplying  certain  of  the 
lamps. 

I  remember  nearly  twenty  years  ago  having  cut  out  tiny  stars 


HAMMER:  PHOSPHORESCENCE.  5 

from  cardboard  and  painted  them  with  luminous  paint,  and 
arranged  them  on  the  ceiling  of  my  bed  room  to  represent  certain 
of  the  principal  constellations  in  the  heavens.  These  stars 
would  absorb  the  light  during  the  day  time,  and  at  night  would 
represent  an  appearance  as  though  the  roof  had  been  removed 
and  one  was  looking  at  the  stars  in  the  sky. 

I  have  here  a  philosophical  toy  which  I  made  years  ago,  with 
which  I  can  show  the  varying  phases  of  the  moon.  I  have  taken 
a  25  cent  globe,  and  painted  half  of  it  with  black  Japan,  as 
representing  the  dark  side  of  the  moon  which  is  never  seen,  the 
other  half  I  have  painted  with  a  number  of  coats  of  luminous 
paint ;  and  by  exciting  the  phosphorescence  of  this  half  by  the 
burning  magnesium,  you  will  see  that  by  slowly  turning  the 
globe  around,  a  perfect  representation  of  the  varying  phases  of 
the  moon  occurs. 

I  hold  in  my  hand  here  a  long  tube  coated  inside  with  sulphide 
of  calcium,  which  makes  a  beautiful  wand,  which  an  orchestra 
leader  might  use  in  a  dark  scene.  I  remember  years  ago  fixing 
up  a  vacuum  tube  and  coil  for  use  as  a  baton  in  the  dark  scene 
in  Gilbert  &  Sullivan's  Opera  of  Ruddigore,  and  fearing  lest 
the  complaisant  leader  be  some  day  knocked  off  his  stool  by  the 
8-inch  coil. 

Here  are  a  couple  of  postal  cards  which  I  secured  in  Europe 
showing  the  Blue  Grotto  at  Capri.  They  are  printed  with  phos- 
phorescent paints;  and  on  exposing  them  to  the  light,  you  will 
see  they  are  exceedingly  pretty. 

Prof.  Dewar  has  shown  that  egg  shells,  feathers,  ivory  and 
paper  become  brilliantly  phosphorescent  if  they  are  cooled  to 
about  200  degrees  below  zero  by  use  of  liquid  air,  and  then 
exposed  to  light.  Many  bodies  seem  to  possess  this  power  of 
absorbing  energy  at  low  temperatures  and  giving  off  light  at 
higher  temperatures.  In  fact,  Dewar  has  observed  that  at  a 
temperature  approximately  that  of  the  boiling  point  of  oxygen 
(184°  C.)  all  bodies,  even  living  tissues,  become  phosphorescent. 

I  have  here  a  collection  of  forty  or  more  glass  tubes  containing 
various  phosphorescent  substances  which,  when  I  burn  this 
magnesium  before  them,  you  will  note  become  brilliantly 
phosphorescent,  showing  red,  yellow,  green,  blue,  and  in 
fact,  all  the  colors  of  the  spectrum.  The  sulphides  of  calcium, 
barium,  strontium,  zinc,  etc.,  largely  enter  into  their  composition. 
I  also  have  here  some  fine  particles  of  fluorspar,  which,  when 
scattered  on  this  hot  plate,  glisten  like  fire  flies. 


6  HAMMER:  PHOSPHORESCENCE. 

A  similar  effect  may  be  produced  by  quinia  or  its  sulphate, 
which  when  spread  on  a  sheet  of  paper  and  laid  on  a  hot  metal 
plate  in  a  dark  room,  shows  a  remarkable  phosphorescence 
which  develops  at  the  edges  and  spreads  to  the  centre. 

Boracic  acid  fused  and  allowed  to  cool  breaks  into  small 
pieces,  and  along  the  cracks  phosphorescent  light  appears. 
Potassium  sulphide  fused  with  cream  of  tartar  shows  the  same 
phenomenon. 

Phosphorescent  ether  may  be  prepared  by  digesting  phos- 
phorus in  ether  for  some  days  in  a  tightly  corked  bottle,  and  when 
a  lump  of  sugar  is  dipped  into  this  and  dropped  into  a  glass  of 
water,  the  surface  appears  quite  luminous. 

The  stream  of  particles,  so  thoroughly  investigated  by  Prof. 
Crookes,  was  given  the  name  of  "Cathode  rays "  by  the  Germans, 
as  a  protest  against  Crookes'  theory  of  molecular  streams  pro- 
pounded by  him  at  the  British  Association  meeting  of  1879; 
Lord  Kelvin  has  told  us  that  the  smallest  particle  which  can  be 
observed  by  the  most  powerful  microscope  contains  18  to  20 
million  atoms,  and  although  until  recently  the  smallest  particle 
we  could  conceive  of  was  the  atom  of  hydrogen,  this  being  the 
lightest  of  gases,  Prof.  J.  J.  Thomson  has  now  shown  us  that 
these  atoms  may  constitute  a  thousand  fragments,  or  as  he  calls 
them,  "corpuscles,"  and  Crookes  showed  us,  and  Villard  of  Paris 
recently  demonstrated  conclusively  that  the  Cathode  rays  con- 
sist of  a  stream  of  these  hydrogen  corpuscles  negatively  charged 
and  moving  at  a  speed  approximating  70,000  miles  per  second; 
and  as  illustrating  the  complexity  of  an  atom,  I  am  reminded  by 
Prof.  Hallock  that  the  late  Prof.  Henry  Rowland  once  said  that 
a  Steinway  grand  piano  was  a  comparatively  simple  piece  of 
mechanism  compared  with  an  iron  atom. 

Prof.  Crookes  has  shown  many  notable  experiments  in  which 
substances  have  been  caused  to  phosphoresce  inside  of  the 
Crookes'  tube  by  the  molecular  bombardment  of  "Cathode 
rays";  and  I  have  here  some  fine  Crookes'  tubes  containing  red 
and  white  coral,  rubies,  calcite,  lava,  etc.,  which  you  will  note 
phosphoresce  finely.  (I  am  indebted  to  Messrs.  Queen  &  Co. 
for  certain  of  these.) 

Prof.  Crookes  has  made  a  diamond  so  phosphorescent 'inside  of 
a  Crookes'  tube,  as  to  give  a  full  candle  power  of  light.  Rubies, 
emeralds,  corals,  fluorspar,  lime  and  many  other  substances 
similarly  phosphoresce,  in  the  Crookes'  tube. 

I  have  here  a  Crookes'  tube  containing  calcined  sea  shells, 


HAMMER:  PHOSPHORESCENCE.  7 

which,  on  connecting  to  the  induction  coil,  is  caused  to  give  off  a 
most  brilliant  light,  and  the  globe  and  contents  to  phosphoresce 
long  after  the  current  is  shut  off. 

Here  again  I  have  a  tube  containing  four  separately  exhausted 
sections,  which  are  filled  with  phosphorescent  substances,  and  a 
tiny  tube  passing  through  all  of  the  partitions  of  the  tubes,  and 
being  connected  with  the  electrodes  at  the  end.  On  connecting 
this  to  the  induction  coil  a  luminous  gaseous  stream  is  seen  in 
the  tiny  tube,  and  the  discharge  accompanying  it  affects  power- 
fully the  phosphorescent  substances  which,  you  will  note,  are 
colored  green,  yellow,  and  blue,  after  the  current  is  shut 
off. 

I  have  here  also  a  Crookes'  "radiometer,"  the  vanes  of  which 
are  painted  with  phosphorescent  substances,  and  on  connecting 
the  radiometer  to  the  coil  the  electricity  rotates  the  vanes  and 
causes  them  to  become  highly  phosphorescent. 

At  a  meeting  of  the  INSTITUTE  on  January  3,  1902,  through 
the  courtesy  of  Mr.  Edison,  I  was  enabled  to  present  some  of 
Mr.  Edison's  tungstate  of  calcium  lamps  which  have  sometimes 
been  called  Edison  X-ray  lamps.  These  lamps  were  Crookes' 
tubes,  the  interior  walls  of  which  were  coated  with  fused  crystals 
of  tungstate  of  calcium,  which  were  caused  to  phosphoresce 
most  dazzlingly  when  they  were  connected  to  an  induction 
coil.  Through  an  accident  to  my  large  coil,  I  was  unable  to  show 
these  tubes  working  as  perfectly  as  I  should  have  liked;  and 
to-night  I  will  show  you  as  an  evidence  of  good  faith  some  of 
them  operating  as  they  should  operate,  and  giving  a  most  power- 
ful light.  Incidentally,  I  am  going  to  show  you  that  this  cannot 
properly  be  called  an  X-ray  lamp  although  a  form  of  X-ray  tube 
is  employed,  as  it  is  not  the  X-rays  outside  but  the  cathode 
rays  inside  of  the  tube  which  produce  the  phosphorescence. 
This  tube  which  I  have  here  and  which  I  have  coated  with 
tungstate  of  calcium  and  platino-barium-cyanide  on  the 
outside,  I  will  now  place  underneath  an  ordinary  Crookes' 
tube,  that  it  may  be  exposed  to  the  X  or  Roentgen  rays;  and 
you  will  see  that  while  the  coated  surface  fluoresces,  as  any 
fluorescent  screen  will  when  exposed  to  Roentgen  rays,  the 
moment  these  rays  cease  there  is  absolutely  no  phosphorescent 
effect,  there  being  no  persistence  of  the  luminescence. 

Now,  another  thing  which  I  think  I  can  show  you  is  that, 
while  cathode  rays  produce  by  their  action  on  the  interior  wall 
of  the  glass  tube  a  secondary  effect  of  ether  pulsations  on  the 


8  HAMMER:  PHOSPHORESCENCE. 

exterior  which  are  Roentgen  or  X-rays,  I  can  now  produce  the 
converse  of  this  by  bombarding  the  outside  of  the  Jtidison  tube 
by  the  Roentgen  rays  from  the  Crookes'  tube,  and  you  will  see 
then  that  I  have  caused  cathode  rays  to  be  stimulated  in  the 
interior  of  the  tube  which  is  merely  held  near  it,  causing  the 
tungstate  of  calcium  to  become  brightly  phosphorescent;  and 
you  will  note  that  I  can  deflect  the  cathode  rays  with  a  mag- 
net. I  believe  this  is  the  first  time  this  conversion  of  Roentgen 
rays  into  cathode  rays  has  been  accomplished  and  is  rendered 
possible  by  this  form  of  tube. 

There  are  many  commercial  applications  which  may  be  made 
of  this  curious  property  of  phosphorescence.  Life  buoys  have 
been  painted  that  they  may  be  seen  when  thrown  overboard; 
sheets  of  cardboard,  such  as  I  have  shown  you,  have  been  used  to 
give  light  in  powder  magazines.  I  have  also  suggested  painting 
projectiles  with  luminous  paint  for  use  at  night;  phosphorescent 
clock  and  watch  dials  have  been  made  in  large  numbers,  and  it 
has  been  suggested  to  make  house  numbers,  door  knobs  and 
escutcheons  for  key  holes  of  such  materials,  cover  the  walls  with 
luminous  paper,  and  even  paint  the  houses  with  luminous  paint. 

The  taps  or  keys  of  incandescent  lamp 'sockets  and  switches 
might  be  made  of  glass  containing  phosphorescent  material,  or 
the  cases  painted  as  I  have  here  done,  so  that  they  could 
readily  be  seen  in  the  dark ;  and  doubtless  certain  phosphorescent 
substances  might  be  used  to  considerable  advantage  in  connec- 
tion with  various  types  of  vacuum  tube  lighting  and  for  vacuum 
tubes  used  in  connection  with  wireless  telegraphy. 

I  hold  in  my  hand  a  tiny  tube  which  I  secured  in  Paris,  which 
contains  what  is  perhaps  the  most  brilliant  phosphorescent  sub- 
stance that  has  yet  been  discovered.  It  is  a  special  preparation 
of  sulphide  of  zinc.  Here  is  a  second  tube  containing  some  of 
the  sulphide  of  zinc,  which  also  has  mixed  with  it  some  radium. 

A  tube  of  this  mixture  may  be  put  away  in  the  dark  for  years, 
and  the  radium  will  act  on  the  zinc,  causing  it  to  phosphoresce 
brilliantly. 

Who  will  say  that  we  shall  not  some  day  find  a  substance 
which  will  be  so  powerfully  acted  upon  by  the  emanations  from 
radium  that  it  may  be  used  as  a  source  of  light  ? 

Here  I  have  a  tube  which  I  have  made  on  the  suggestion  of 
Prof.  Curie,  consisting  of  two  bulbs  with  a  stop  cock  between. 
in  one  of  which  may  be  placed  sulphide  of  zinc,  or  similar  sub- 
stances, and  in  the  other  radium;  and  in  this  manner  the  radio- 
activity of  various  substances  may  thus  be  investigated. 


HAMMER:  PHOSPHORESCENCE.  9 

A  tube  containing  chloride  or  bromide  of  silicon  and  exhausted 
to  12  or  15  mm.,  and  sealed,  will  when  rubbed  briskly  with  silk 
glow  in  one  case  a  rose  color  and  in  the  other  a  greenish  yellow. 

I  hold  in  my  hand  here  two  Geisler  tubes,  each  containing  an 
inner  tube  with  beaded  surfaces.  In  each  of  the  outer  tubes 
is  a  small  amount  of  quicksilver;  and  in  one  tube  nitrogen  gas, 
and  in  the  other  carbonic  acid  gas.  By  shaking  these  tubes 
rapidly  the  friction  of  the  quicksilver  against  the  glass  produces 
electricity,  which  causes  the  gas  to  become  luminescent. 
Various  other  gases  may  be  thus  employed,  producing  different 
color  effects. 

It  has  been  suggested  that  life  buoys  could  be  equipped  with  a 
number  of  mercury  tubes,  circular  or  otherwise,  and  set  in  differ- 
ent positions,  so  that  the  rolling  of  the  buoy  in  the  sea  would 
constantly  agitate  the  mercury  and  render  the  tubes  luminous. 

Here  is  a  tube  containing  mercurial  salts,  which  changes 
greatly  the  color  of  its  phosphorescence  by  heating  the  tube  in 
'alcohol  flame. 

In  this  box  I  have  a  large  spiral  glass  tube  which  is  expanded 
into  bulbs  at  various  points  throughout  its  length.  This  tube, 
for  which  I  am  indebted  to  my  friend  Dr.  Geyer,  contains  sul- 
phuric anhydride;  and  you  will  note  when  I  connect  this  to  the 
induction  coil  and  send  a  discharge  of  electricity  through  it  that 
the  gas  inside  of  the  tube  becomes  phosphorescent  and  remains 
so  for  a  considerable  period  after  the  electricity  is  cut  off. 

I  have  here  a  bottle  containing  phosphorus  and  olive  oil,  which 
you  will  see  becomes  most  brilliantly  phosphorescent  when  I 
withdraw  the  stopper,  and  allow  the  air  to  enter  the  bottle.  The 
phosphorescence  in  this  case  is  due  to  combustion,  or  to  the 
oxidation  of  the  liquid.  I  can  also  write  phosphorescent  char- 
acters on  this  ground  glass  plate  wet  in  hot  water  with  this  stick 
of  phosphorus.  Other  forms  of  phosphorescence  are  caused  by 
chemical  changes  or  the  slow  combustion  of  decaying  vegetable 
matter  or  decaying  fish. 

Occasionally  clouds  show  a  phosphorescent  light  at  night; 
snow  is  phosphorescent  after  exposure  to  sunlight,  and  no  doubt 
many  substances  retain  during  the  night  the  phosphorescent 
light  imparted  by  the  sun's  rays  during  the  day. 

There  are  also  many  insects,  such  as  fire  flies  and  glow  worms, 
and  many  deep  sea  fishes  which  have  the  properties  of  producing 
phosphorescence.  Phosphorescence  is  exhibited  among  other 
animals  by  the  infusorian  noctiluca,  marine  radiates,  polyps,  etc., 
which  are  the  principal  causes  of  phosphorescence  of  the  sea 


II) 


HAMMER:  PHOSPHORESCENCE. 


In  Fig.  1,  is  shown  an  illustration  of  the  "Pyrophorus  Noc- 
tilucus."  This  tropical  beetle  has  been  most  carefully  studied 
by  Prof.  S.  P.  Langley  and  F.  W.  Very,  and  the  efficiency  of  the 
light  given  off  tested  by  the  Langley  bolometer;  and  they  have 
demonstrated  that  practically  all  the  energy  which  its  phosphor- 
escence represents,  appears  as  light;  and  the  light  given  off  by 
this  insect  is  the  most  efficient  light  known,  it  being  produced  at 
about  one  four-hundredth  part  of  the  cost  of  the  energy  which  is 
expended  in  the  candle  flame*. 

Sir  Oliver  Lodge  says  if  the  secret  of  the  firefly  were  known,  a 
boy  turning  a  crank  could  furnish  sufficient  energy  to  light  an 
entire  electric  circuit. 

And  Prof.  Langley  says,  "There  seems  to  be  no  reason  why 
we  are  forbidden  to  hope  that  we  may  yet  discover  a  method 
(since  such  a  one  certainly  exists  and  is  in  use  on  the  small  scale) 


FIG.    1.— "Pyrophorus   Noctilucus"    (life  size),   the   Producer  of  the 
Cheapest  Form  of  Light  Known. 

of  obtaining  an  enormously  greater  result  than  we  now  do  from 
our  present  means  of  producing  light." 

Langley  believes  the  light  of  these  insects  is  due  to  chemical 
action,  as  it  is  decreased  by  nitrogen  which  checks  combustion, 
and  is  increased  by  oxygen  which  increases  combustion,  and 
furthermore,  the  product  is  apparently  carbon  dioxide. 

We  also  may  produce  phosphorescence  by  rubbing  crystals 
together,  or  by  friction  of  other  bodies,  or  by  cleavage,  such  as 
fracture  of  lump  sugar  in  the  dark. 

Among  plants,  phosphorescence  was  first  recorded  by  A.  Lin- 
naeus, whose  daughter  discovered  it  in  the  nasturtium.  Phosphor- 

*  "O"  the  Cheapest  Form  of  Light, "  by  S.  P. 
No.  1258  Smithsonian  Misc.  Coll. 


HAMMER:  RADIUM.  11 

escence  or  flashes  of  light  are  of  ten  observed,  especially  just  after 
sunset,  in  the  common  red  and  yellow  marigold,  the  tuberose, 
sunflower,  poke  weed,  martagon-lily  and  the  poppy.  The  root 
stock  of  khus-khus  grass  and  the  sap  of  certain  tropical  vines 
and  subterranean  plants,  some  liverworts,  ferns,  mosses,  fungi 
and  algae,  and  the  mycelium  of  fungi  in  decaying  wood  phos- 
phoresce. This  phosphorescence  is  said  to  be  due  to  slow 
decay  and  oxidation,  either  in  the  mycelia  or  fructifications  of 
the  fungi.  Heat  and  dryness  soon  dissipate  it. 

Having  considered  certain  of  the  phenomena  of  phosphor- 
escence and  fluorescence,  I  wish  now  to  call  your  attention  to 
these  remarkable  substances  which  have  recently  been  dis- 
covered, which  give  off  light  the  moment  they  are  created,  with- 
out having  to  be  stimulated  by  any  form  of  heat,  light,  electrical 
or  other  vibrations,  so  far  as  we  are  at  present  cognizant  of,  and 
these  substances  are  attracting  a  great  deal  of  attention,  and  are 
likely  to  teach  us  more  about  the  constitution  of  matter,  and  the 
co-relation  of  the  vital  and  physical  forces,  than  any  substances 
which  have  been  created  since  the  world  began.  I  refer  to 
"Radium,  Polonium,  Actinium  and  Thorium." 

RADIUM  AND  OTHER  RADIOACTIVE  SUBSTANCES. 

To  the  discovery  of  M. 
Henri  Becquerel,  member  of 
the  INSTITUTE  of  France,  in 
1896,  of  those  remarkable 
radiations  emanating  from 

iNlif^^  uranium,  the  science,  if  we 

may  so  term  it,  of  radioac- 
tivity, owes  its  foundation. 

Great  importance  must, 
however,  be  attached  to  the 
previous  investigations  into 
the  phenomena  produced  on 
the  interior  and  exterior  of 
vacuum  tubes  of  various 
kinds  by  such  men  as  Varley, 
PROF.  HENRI  BECQUEREL.  Hittorf,  Crookes,  Lenard, 

From  a  portrait  presented  to  the  author.          Roentgen,  Hertz,  J.  J.  Thom- 

son,  Goldstein,  Schmidt,  Ebert,  Wiechert,  Geissler,  Kaufmann, 
Puluj,  Perrin,  Villard,  Wien,  Wiedemann,  Majorana,  Birkland, 
Deslandres,  Poincare",  Edison,  Tesla,  Rowland,  Michelson 


12  HAMMER:  RADIUM. 

E.  Thomson,  Moore,  Rollins,  Campbell-Swinton,  and  others, 
which  investigations  had  already  wrested  from  Nature  so  many 
secrets  bearing  upon  the  constitution  of  matter  and  paved  the 
way  for  the  Becquerel  rays. 

Two  important  links  in  the  chain  were  supplied  by  the  experi- 
ments of  M.  Henry1  and  M.  Niewenglowski2.  The  former  showed 
that  phosphorescent  sulphide  of  zinc  penetrated  black  paper  and 
affected  a  photograph  plate,  similar  to  Roentgen  rays;  and  the 
latter  in  his  experiment  replaced  the  usual  cover  of  a  loaded 
photographic  plate  holder  by  a  thin  sheet  of  aluminum ;  on  top 
of  this  he  placed  four  glass  squares  sprinkled  over  with  sulphide 
of  calcium  rendered  phosphorescent  by  exposure  to  sunlight.  A 
jeweller's  glass  bell  jar  was  put  over  each  plate,  and  the  whole 
apparatus  was  then  placed  in  a  dark  room  for  twenty-three  hours. 
On  developing  the  negative,  the  plate  showed  an  excellent  image 
of  the  squares  of  glass  and  the  bell  glass  covers  which  had  been 
made  through  the  aluminum,  a  substance  heretofore  supposed 
to  be  entirely  opaque  to  light,  the  white  line  shown  bordering  the 
squares  of  glass  (where  the  plate  had  not  been  affected)  indicated 
that  the  rays  had  here  been  bent  or  refracted  in  passing  through 
the  edge  of  the  glass,  demonstrating  that  he  was  only  dealing 
with  ordinary  light  rays. 

Subsequently,  Prof.  Becquerel  investigated  the  effect  of  phos- 
phorescent substances  on  photographic  plates  covered  with 
black  paper,  such  as  is  used  for  covering  X-ray  plates ;  and  which 
while  transparent  to  X-rays  is  impervious  to  ordinary  light  waves 
(a  plate  so  protected  may  be  left  in  the  sunlight  for  twenty-four 
hours) ;  and  he  exposed  various  uranium  salts  to  sunlight  to  try 
their  effect,  at  times  placing  an  aluminum,  copper  or  glass  plate 
between  the  paper  and  the  photograph  plate  or  film.  On  one 
occasion  after  he  had  placed  some  double  sulphate  of  uranium 
and  potassium  on  a  photographic  plate,  the  weather  became 
stormy,  and  he  placed  his  plate  with  the  uranium  salts 
upon  it  in  a  drawer,  where  it  remained  for  several  days  on 
account  of  continuance  of  the  cloudy  weather.  It  then  occurred 
to  him  to  develop  the  plate;  and  much  to  his  surprise  he  found  a 
well-defined  impression  upon  the  plate,  and  this  caused  without 
any  effect  of  phosphorescence  due  to  exposure  to  sunlight.  This 


1.  Comptes  Rendus,  Feb.  10,  1896      Vol.  cxxii.,  p.  312 

2.  Ibid.,  cxxii.,  p.  386. 


HAMMER:  RADIUM.  13 

led  to  his  discovery  and  investigation  of  the  remarkable  radia- 
tions which  have  since  been  known  by  his  name*. 

I  have  here  some  samples  of  the  first  substances  employed  by 
Becquerel,  consisting  of  double  sulphate  of  uranium  and  potas- 
sium and  double  sulphate  of  uranium  and  ammonium,  for  which 
I  am  indebted  to  the  courtesy  of  Dr.  C.  F.  Chandler,  of  Columbia 
University. 

Peligot  in  1840  succeeded  in  isolating  metallic  uranium  from 
the  chloride.  Well  known  forms  of  it  are  also  uranium  arsenate, 
uranium  carbonate,  uranium  niobate,  uranium  phosphate, 
uranium  silicate  and  uranium  sulphate.  Uranium  was  first 
discovered  in  1789  by  the  German  chemist  Klaproth,  he  naming 
it  after  the  planet  "  Uranus."  I  have  here  various  forms  of  this 
uranium  and  also  some  metallic  uranium  prepared  in  the 
electric  furnace  by  Moissan,  which  is  more  powerful  than  any 
other  form  of  uranium. 

Uranium,  although  widely  distributed,  is  never  found  in  large 
amounts,  and  forms  several  minerals.  The  commonest  of  these 
is  "uraninite,"  commonly  known  as  "pitchblende,"  which  is  a 
compound  oxide  containing  81^  per  cent,  of  uranium,  4  per  cent, 
of  lead  and  ^  per  cent,  of  iron  with  oxygen  and  water,  and  some- 
times magnesia,  manganese  or  silica. 

The  pitchblende  which  contains  the  largest  percentage  of 
radioactive  material,  which  has  thus  far  been  discovered,  is  the 
Bohemian  pitchblende.  It  is  also  found  in  Saxony  in  small 
pockets,  and  a  distinct  vein  of  it  has  been  found  in  Cornwall, 
England.  Prof.  Curie  informed  the  writer  that  he  had  secured 
some  excellent  radioactive  pitchblende  from  the  United  States 
(Colorado). 

The  ore  as  mined  in  Cornwall  yields  18  per  cent,  to  20  per  cent, 
of  the  metal,  this  being  the  most  important  source,  and  this  is 
usually  put  on  the  market  in  the  form  of  uranium  sesqui-oxide, 
and  is  largely  used  for  giving  porcelains  a  velvety  black  when 
heated  in  the  annealing  fire,  and  to  some  extent  for  imparting  a 
greenish  yellow  fluorescence  to  glass.  It  has  also  been  suggested 
to  utilize  it  on  account  of  its  high  resistance  in  connection  with 
incandescent  lighting. 

Following  the  original  discovery  of  the  Becquerel  radiations  in 
1896,  came  the  discovery  in  1898  of  "Polonium,"  by  Prof.  Pierre 
Curie  and  Mme.  Sklodowska  Curie,  who  in  investigating  Becquerel 

*  Comptes  Rendus,  Feb.  24,  1896.     Vol.  cxxii.,  p.  420. 


14  HAMMER:  RADIUM. 

radiations  from  uranium  found  some  samples  of  pitchblende, 
from  which  the  uranium  is  extracted,  which  was  much  more 
powerful  than  any  uranium  they  had  found,  being  four  times  the 
radioactivity  of  metallic  uranium.  Concluding  naturally  that 
the  Becquerel  radiations  were  due  to  some  unknown  substance  in 
the  pitchblende  they  commenced  a  most  painstaking  search 
for  it,  and  discovered  a  substance  associated  with  bismuth, 
which  it  resembled  very  much  in  its  chemical  characteristics,  to 
which  Mme.  Curie  gave  the  name  "Polonium,"  after  her  native 
land,  Poland. 

I  have  here  perhaps  the  only  sample  in  this  country  at  present 
of  metallic  polonium,  which  in  color  resembles  somewhat  the 
particles  of  nickel ;  and  here  also  is  some  sub-nitrate  of  polonium. 
Where  substances  are  referred  to  as  possessing  a  certain  "ra- 
dioactivity," for  instance  300,  it  means  that  the  radiations  are 
300  times  as  powerful  as  the  original  radiations  emanating  from 
uranium,  which  were  discovered  by  Becquerel,  and  which  are 
taken  as  a  standard  of  comparison. 

The  two  tubes  which  I  have  here  to-night  are  of  the  sub-nitrate 
and  metallic  form,  and  possess  a  radioactivity  of  only  about  300. 
The  sub-nitrate  form  is  a  white  powder,  and  the  metallic,  as  said, 
resembles  in  appearance  particles  of  nickel. 

Polonium  is  precipitated  by  hydrogen  sulphide. 
Polonium  apparently  loses  its  power  much  more  rapidly  than 
radium;  and  the  Curies  have  not  been  able  to  prepare  any  in 
which  the  rays  have  been  deviable,  although  Giesel  has  prepared  a 
form  possessing  both  deviable  and  non-deviable  rays.  And 
Elster  states  that  when  polonium  is  placed  in  a  vacuum,  the  rays 
may  be  deviated  by  a  magnet  to  a  greater  extent  than  those  of 
radium. 

Polonium  passes  more  rays  through  aluminum  than  do  the  rays 
from  uranium ;  but  Crookes  has  shown  that  they  do  not  penetrate 
glass,  as  in  the  case  of  radium,  and  they  are  readily  absorbed  by 
minerals,  and  readily  cut  off  by  thin  paper.  They  are  readily 
absorbed  by  quartz,  fluoride  and  mica,  whereas  these  substances 
are  freely  penetrated  by  both  radium  and  uranium. 

In  the  same  year  in  which  polonium  was  discovered  those 
remarkable  investigators,  M.  and  Mme.  Curie  and  M.  Bemont 
rttcceeded  in  isolating  a  second  substance  found  in  pitchblende! 
which  was  associated  with  barium  and  possessed  many  of  the 
chemical  and  other  characteristics  of  that  substance,  and  to  this 
they  gave  the  name  " Radium."  Of  this  we  shall  treat  later 


HAMMER:  KADIUM. 


15 


16  HAMMER:  RADIUM. 

In  1899  was  discovered  the  third  substance  in  pitchblende, 
which  possessed  the  chemical  and  other  characteristics  of  thorium 
with  which  it  was  associated,  and  to  this  Debierne  gave  the  name 
"Actinium."  It  is  precipitated  by  ammonium  sulph-hydrate. 
Crookes  states  that  actinium  is  identical  with  the  substance 
which  he  had  isolated  from  uranium  and  to  which  he  gave  the 
name  "uranium  X."  The  rays  from  actinium  are  de viable. 

Of  the  three  substances  to  which  I  have  referred,  radium  is  by 
far  the  most  important  and  is  of  extraordinary  interest.  It  is 
doubtful  whether  any  substance  has  been  discovered  in  the  his- 
tory of  the  world  of  such  stupendous  interest  and  importance  and 
possessing  such  puzzling  characteristics  as  radium,  which  seems 
so  at  variance  with  well-established  scientific  theories  as  to  the 
constitution  of  matter. 

In  Fig.  2  are  shown  in  consecutive  order  from  left  to  right, 
a  tube  containing  pitchblende,  or  uraninite,  from  which  radium, 
polonium  and  actinium  as  well  as  uranium  are  extracted ;  a  tube 
containing  metallic  uranium  made  in  the  electric  furnace  by 
Moissan ;  two  flasks  containing  double  sulphate  of  uranium  and 
potassium;  and  double  sulphate  of  uranium  and  ammonium, 
these  being  the  original  salts  of  uranium  with  which  Becquerel 
experimented  when  he  discovered  the  Becquerel  rays;  a  tube 
containing  thorium,  the  most  radioactive  substance  next  to 
radium;  two  tubes  of  polonium  and  bismuth,  one  tube  of 
metallic  polonium  and  the  other  sub-nitrate  of  polonium; 
seven  tubes  of  chloride  of  radium  associated  with  barium  rang- 
ing in  radioactivity  from  40  to  7,000;  a  tube  containing  radium 
and  phosphorescent  sulphide  of  zinc;  and  a  tube  containing 
carnotite,  which,  together  with  the  samples  shown  of  uraninite, 
autunite,  torbernite,  gummite,  and  fergusonite,  are  among  the 
mineral  substances  which  are  rich  in  radioactive  materials. 
Other  active  minerals  are  orangite,  euxenite,  broggerite,  cleveite, 
monazite,  samarskite,  xenotime,  aeschynite,  niobite,  arrhenite, 
hielmite,  sipilite,  chalcolite,  etc. 

In  Fig.  3  the  two  tubes  of  polonium  and  the  seven  tubes  of 
radium  are  shown  about  two-thirds  their  natural  size. 

Radium,  actinium  and  polonium,  Prof.  Curie  states,  possess 
an  activity  which  is  a  million  times  that  of  uranium.  Prof. 
Curie  says  radium  cm'.ts  exactly  the  same  quantity  of 
Becquerel  rays  when  in  the  liquid  air  as  it  does  at  normal  tem- 
perature of  the  atmosphere.  The  luminosity  of  the  chloride  of 
radium  is  strongar  in  the  liquid  air  than  in  the  atmosphere  at  a 
normal  temperature. 


HAMMER-  RADIUM. 


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HAMMER:  RADIUM. 


My  friend,  Mr.  R.  R.  Bowker,  whom  I  met  in  Paris  last  Fall,! 
told  the  writer  that  he  had  shortly  before  that  been  dining  seated  I 
between  Lord  Kelvin  and  Prof.  Becquerel,  and  that  Lord  Kelvin  ; 
had  turned  to  him  and  said,  that  the  discovery  of  Becquerel  j 
radiations  had  placed  the  first  question  mark  against  the  principle  | 
of  conservation  of  energy  which  had  been  placed  against  it  since 
that  principle  was  enunciated. 

Within  the  past  month  great  interest  has  been  attracted  by  the 
statement  made  by  Profs.  Curie  and  Laborde  that  radium  main-  1 
tains  its  own  temperature  at  1 .5  Centigrade  above  its  surroundings, 
this  being  equivalent  to  stating  that  half  a  pound  of  radium  salt 
would  evolve  in  one  hour  sufficient  heat  to  equal  that  caused  by  the 
burning  of  one-third  of  a  cubic  foot  of  hydrogen  gas ;  and  that  the 
heat  evolved  from  pure  radium  salt  is  sufficient  to  melt  more  than  - 
its  own  weight  of  ice  every  hour.     This  evolution  of  heat,  it  is 
claimed,  is  going  on  constantly  for  indefinite  periods  and  leaving  ; 
the  radium  at  the  end  of  months  of  activity  as  potent  as  it  was 
at  the  beginning.     The  problem  therefore  confronts  the  world  of 
solving  how  radium  can  constantly  throw  off  heat  without  com- 
bustion or  without  chemical  change,  as  Prof .  Curie  says  it  does. 

Messrs.  Curie  and  Laborde  employed  a  thermo-electric  couple 
of  iron  and  constantin,  one  of  whose  junctions  is  surrounded 
by  radioactive  barium  chloride  and  the  other  by  pure  barium 
chloride.  They  used  two  small  bulbs  of  the  same  dimensions, 
one  containing  one  gramme  of  radiferous  barium  chloride  con- 
taining about  one-sixth  of  its  weight  in  radium  chloride  and 
the  other  bulb  containing  one  gramme  of  pure  barium  chloride. 

The  junctions  of  the  thermo-electric  couple  are  respectively 
placed  in  the  center  of  each  bulb,  surrounded  by  the  substances. 
The  bulbs  are  isolated  in  air  within  the  center  of  two  small 
identical  enclosures,  surrounded  in  turn  by  a  third,  which  is 
thermally  insulated,  and  maintains  itself  at  a  practically  uniform 
temperature,  and  under  these  conditions  variations  in  the  sur- 
rounding temperature  are  felt  in  the  same  manner  at  both 
junctions  and  do  not  affect  the  indications  of  the  couple.  Messrs. 
Curie  and  Laborde  both  thus  observed  a  difference  of  tempera- 
ture of  1.5  degrees  C.- between  the  radiferous  barium  chloride 
and  the  pure  barium  chloride,  the  former  having  the  higher 
temperature.  (Comptes  rendus,  March  16,  1903.) 

In  a  letter  recently  received  by  the  author  from  Prof.  Curie 
bearing  upon  the  question  of  heat  given  off  by  radium  Prof. 
Curie  writes  as  follows:  "Since  the  time  I  had  the  honor  to  see 


HAMMER:  RADIUM.  19 

you  at  our  School  of  Physics  and  Chemistry  I  have  continued 
to  investigate  into  the  radioactivity  induced  by  radium  and  the 
way  that  radioactivity  is  disappearing  in  the  course  of  time. 

"In  a  study  of  another  kind  (in  collaboration  with  M. 
Laborde)  I  found  that  the  radium  is  setting  off  heat  continually 
and  in  a  very  large  amount ;  each  gramme  of  the  radium  is  set- 
ting off  in  each  hour  100  small  calories,  or  in  other  words  it  is 
setting  off  heat  enough  to  melt  in  each  hour  its  own  weight  in  ice. 

"Where  is  the  source  of  this  energy?  Both  Mme.  Curie  and  my- 
self are  not  able  to  go  beyond  some  hypothesis;  one  of  these 
consists  in  supposing  the  atoms  of  radium  evolving  and  trans- 
forming into  another  simple  body  and  despite  the  extreme 
slowness  of  that  transformation  which  cannot  be  located  during 
a  year;  the  amount  of  energy  involved  in  that  transformation 
is  tremendous. 

"  The  second  hypothesis  consists  in  the  supposition  that 
radium  is  capable  of  capturing  and  utilizing  some  radiations  of 
unknown  nature  which  cross  the  space  without  our  knowledge." 

Profs.  J.  J.  Thomson  and  Rutherford  advance  the  theory  that 
there  is  a  succession  of  chemical  changes  going  on  causing  the 
spontaneous  projection  of  larger  masses  of  material  at  enor- 
mous velocities,  and  that  while  certain  portions  are  constantly 
dying  out  and  becoming  inert  other  portions  are  constantly  in- 
creasing in  strength  and  power. 

Someone  has  remarked  that  for  years  we  have  been  extracting 
uranium  oxides,  and  pouring  down  the  waste  pipes  and  into  the 
dust  bins  the  more  interesting  and  precious  radioactive  sub- 
stances. 

Although  radium,  polonium  and  actinium  have  been  termed  new 
elements,  in  the  case  of  polonium  and  actinium,  they  have  as  yet 
not  been  found  in  sufficiently  pure  state  and  in  sufficient  quantity 
to  give  a  spectrum,  and  to  prove  conclusively  that  they  are  new 
elements.  Prof.  Curie  has,  however,  stated  emphatically  that 
there  is  now  no  doubt  of  radium  being  a  new  element. 

The  tiny  brown  bulb  which  I  hold  in  my  hand  is  the  duplicate 
of  the  one  which  Prof.  Curie  showed  me  at  his  laboratory  last 
Fall,  which  contained  the  only  sample  of  chemically  pure  radium 
in  the  world,  this  being  between  two  and  three  one-hundredths  of 
a  gramme ;  and  it  was  the  spectrum  of  that  sample,  showing  only 
the  lines  characteristic  of  radium,  as  tested  by  Demarcay,  which 
demonstrated  it  to  be  a  new  element.  And  with  this  sample, 
also,  the  atomic  weight  for  radium  of  225  was  determined.  The 


20  HAMMER:  RADIUM. 

atomic  weight  of  the  barium  heretofore  always  associated  with 
radium,  but  which  in  this  sample  had  been  eliminated,  is  but  157. 

In  answer  to  my  inquiry  as  to  its  value,  Prof.  Curie  said  that 
100,000  francs  ($20,000)  could  not  purchase  this  tiny  sample. 
'  I  was  enabled  through  the  courtesy  of  Prof.  Curie  to  secure  from 
the  Societe  Centrale  des  Produits  Chimique  of  Paris,  some  nine 
different  preparations  of  radium  and  two  of  polonium,  which  I 
have  here  for  your  consideration.  I  was  unable  to  secure  any 
actinium ;  in  fact,  but  a  trace  of  this  substance  has  thus  far  been 
secured. 

If  the  lights  are  extinguished,  and  you  will  sit  for  a  few  mo- 
ments in  the  dark,  I  will  pass  these  tubes  about  the  room  that 
you  may  observe  the  bright  light  given  off  by  certain  of  them. 
These  samples  which  I  have  range  from  forty  times  the  radio- 
activity of  uranium  (which  is  taken  as  a  standard),  up  to  7,000. 

The  laboratory,  where  these  substances  are  prepared,  is  undei 
the  control  of  Prof.  Curie;  and  up  to  recent  date,  all  radium  of 
higher  radio-activity  than  7,000  has  been  retained  for  the 
experiments  of  M.  and  Mme.  Curie  and  their  associates;  but  I 
received  a  letter  recently  from  Director  P.  Boulay  of  the  Societe 
Centrale,  in  which  I  was  informed  that  they  will  shortly  put 
upon  the  market  a  preparation  of  radium,  chemically  pure  or 
nearly  so,  at  a  cost  of  30,000  francs  ($6,000)  per  gramme  or 
about  $2,721,555.90  per  pound. 

Radium,  while  it  has  been  spoken  of  as  a  metal,  has  never 
been  secured  in  a  metallic  form,  the  usual  form  being  as  a 
chloride  or  bromide. 

Prof.  Curie  told  the  writer  that  the  result  of  all  the  work  done 
in  Germany  and  France  in  the  past  three  years  had  only  resulted 
in  the  securing  of  about  one  pound  of  radium ;  this  including  all 
grades  or  qualities.  Prof.  J.  J.  Thomson  says  there  is  far  more 
gold  in  sea  water  than  there  is  radium,  polonium  and  actinium 
in  pitchblende. 

Prof.  Curie  took  this  ring  which  I  have  on  my  hand,  which 
contains  a  small  diamond,  into  his  dark  room  and  holding  near 
it  a  small  pill  box  containing  about  a  gramme  of  radium,  caused 
the  stone  to  phosphoresce  most  beautifully.  It  was  as  if  a 
lighted  candle  had  been  brought  near  to  it.  Prof.  Curie  re- 
marked that  this  showed  that  the  stone  was  a  genuine  diamond ; 
and  if  it  had  been  paste  there  would  have  been  no  effect  produced, 
and  that  radium  therefore  constituted  an  excellent  means  for 
testing  the  genuineness  of  diamonds. 


HAMMER:  RADIUM.  21 

According  to  M.  and  Mme.  Curie,  radium  rays  act  in  many  ways 
like  light.  They  reduce  silver  salts,  peroxide  of  iron  and  bi- 
chromate of  potash  in  presence  of  organic  substances;  they 
also  color  glass,  porcelain  and  white  paper,  and  they  transform 
greenish  yellow  platino-cyanide  of  barium  into  a  brown  variety. 
Giesel  had  prepared  platino-cyanide  of  barium  with  a  trace  of 
radium.  This  spontaneously  became  brown,  and  it  then  polar- 
ized light  like  tourmaline.  He  also  found  that  this  colored  rock 
salt  just  as  cathode  rays  do,  or  the  vapors  of  alkaline  metals,  and 
furthermore  showed  that  radium  salts,  brought  near  the  temples 
or  to  the  closed  eyes,  produced  a  sensation  of  light. 

M.  Becquerel,  referring  to  the  chemical  action  of  radium  rays, 
says  that  radium  and  uranium  rays  act  upon  silver  gelatino- 
bromide,  but  produce  no  effect  upon  Daguerre  plates,  or  upon 
photographic  papers,  and  says  that  colorations  of  glass,  porce- 
lain, paper  and  certain  crystals,  as  well  as  the  painful  physio- 
logical effects  also  belong  to  this  class  of  phenomena.  He  also 
calls  attention  to  the  transformation  of  white  into  red  phosphorus 
in  24  hours,  the  reduction  of  mercuric  chloride  in  the  presence  of 
oxalic  acid  with  the  precipitation  of  calomel,  and  finally  the 
destruction  of  the  germination  power  of  seeds  after  long  exposure. 
Becquerel  also  shows  that  radium  rays  possess  the  same  power 
as  the  electric  spark,  or  the  prolonged  action  of  violet  or  ultra- 
violet rays,  of  restoring  the  phosphorescent  properties  under  ex- 
posure to  heat  of  a  body  deprived  of  them  by  over-heating. 

Practically  all  the  radium  which  has  thus  far  reached  this 
country,  with  the  exception  of  that  in  the  possession  of  the 
author,  has  been  the  German  radium,  and  Prof.  Curie  tells  the 
writer  that  he  had  tested  all  of  the  German  productions,  and  he 
has  found  none  of  them  to  exceed  a  radioactivity  of  300. 

De  Haen  of  Seelze  near  Hanover,  Germany,  and  Giesel,  of 
Brunswick,  also  have  manufactured  radium.  De  Haen  recently 
informed  the  writer  that  the  preparations  he  puts  on  the  market 
cost  ten  and  thirty  shillings  per  gramme. 

As  indicative  of  the  enormous  difficulties  to  be  encountered  in 
procuring  this  wonderful  substance,  it  is  interesting  to  note  that 
it  takes  5,000  tons  of  uranium  residues  to  produce  a  kilo  (2.2 
pounds)  of  radium;  and  the  cost  of  handling  these  residues  is 
$2,000  per  ton.  To  secure  the  chemically  pure  radium  is  enor- 
mously expensive,  and  it  would  be  impossible  to  do  this  by  chemi- 
cal analysis,  therefore  the  far  more  sensitive  electrical  method  is 
employed,  and  the  Curies  say  that  they  can  detect  the  presence 


22  HAMMER:  RADIUM. 

of  a  radioactive  substance  by  the  means  of  such  a  minute  quan- 
tity that  it  would  require  5,000  times  this  amount  to  show  at  all 
in  the  spectroscope.  And  it  is  stated  that  this  method  of  elec- 
trical analysis  is  thousands  of  times  more  sensitive  than  spectrum 
analysis  and  millions  of  times  more  sensitive  than  chemical 

analysis. 

In  Fig.  4  is  shown  the  "electrometer"  method  with  which  tl 
Curies  have  studied  the  radioactivity  of  different  substances.  It 
consists  of  two  plates,  A  and  B,  on  the  latter  of  which  is  placed  the 
radioactive  substance  to  be  tested.  This  makes  the  air  a  con- 
ductor of  electricity  between  the  two  plates,  and  for  measuring 
this  degree  of  conduct ibility,  the  plate  B  is  brought  to  a  high 
potential  by  connecting  it  to  one  side  of  the  storage  battery  P,  the 


FIG.  4. — Apparatus  employed  by  M.  and 
Mme.  Curie  in  the  study  of  radio- 
activity. 


other  side  of  which  is  connected  to  the  ground.  If  the  plate  A  is 
brought  to  the  potential  of  the  ground  by  the  wire  C-D,  an  electric 
current  begins  to  flow  between  the  two  plates,  A  and  B.  The 
potential  of  plate  A  is  shown  by  the  electrometer  E.  If  we  cut  this 
communication  with  the  ground  at  c,  the  plate  A  becomes  charged 
causing  the  electrometer  to  deviate.  The  speed  deviation  is 
proportionate  to  the  intensity  of  the  current  and  can  serve  for 
measuring  it.  But  it  is  preferable  to  make  this  measurement  by 
compensating  the  charge  taken  by  plate  A,  so  that  the  elec- 
trometer remains  at  zero.  The  charges  which  are  extremely 
feeble  can  be  compensated  by  means  of  a  Piezo-electric  quartz  Q, 


HAMMER:  RADIUM. 


23 


one  armature  of  which  is  connected  with  the  plate  A,  and  the  other 
armature  grounded.  The  quartz  plate  is  given  a  certain  tension 
by  weights  placed  on  the  plate  H.  This  tension  is  gradually 
produced  and  gives  a  charge  of  a  definite  quantity  of  electricity 
which  can  be  measured.  The  operation  may  be  so  regulated 
that  there  is  a  constant  compensation  between  the  quantity  of 
electricity  which  passes  through  the  condenser  and  that  of  the 
opposite  sign  furnished  by  the  quartz.  So  we  can  measure  in  an 
absolute  value  the  quantity  of  electricity  passing  through  the 
condenser  in  a  certain  time. 

Doubtless  some  loss  is  caused  by  the  rays  which  pass  directly 
through  the  condenser  plates. 


FIG.  5. — Curie's  Electroscope  for  the  study  of  Radio-activity. 


Dolezalek  has  designed  a  very  sensitive  type  of  electrometer 
built  by  B artels  of  Gottingen,  a  description  of  which  may  be 
found  in  Verk.  der  Deutsche  Physik  Ges.,  Hi  (1901). 

It  is  well  known  that  the  leaves  of  a  gold  or  aluminum  foil 
electroscope  will  hold  their  charge  in  dry  air  indefinitely ;  but  the 
Becquerel  rays  are  found  to  dissipate  the  charge  by  ionization  of 
the  air,  or  rendering  the  air  a  conductor  of  electricity  (the 
electroscope  may  also  be  discharged  by  Roentgen  rays,  cathode 
rays  and  ultra-violet  light). 

In  Fig.  5  is  shown  a  form  of  electroscope  devised  by  the  Curies 
for  the  study  of  radioactive  substances.  Referring  to  the  dia- 
gram to  the  right,  it  will  be  noted  that  the  electroscope  consists 
of  a  single  movable  sheet  of  gold  or  aluminum  foil  attached  to  a 
stationary  sheet  of  copper  L,  being  supported  by  the  insulating 


24  HAMMER:  RADIUM. 

piece  1  The  radioactive  substance  to  be  tested  is  placed  on  the 
lower  of  the  disks  P  and  P',  preferably  on  a  removable  plates 
The  radiations  make  the  air  a  conductor  between  these  two  plates. 
The  electroscope  is  charged  by  means  of  a  stick  of  ebonite  rubbed 
briskly  and  placed  near  the  rod  B.  This  deflects  the  sheet  L 
from  the  vertical  and  it  so  remains  for  a  very  long  time.  When 
radioactive  substances  are  brought  near  it,  the  gold  or  aluminum 
leaf  is  caused  to  lose  its  charge,  and  the  leakage  is  observed  by 
means  of  a  stationary  telescope  shown  in  the  left  hand 
figure,  which  is  provided  with  a  micrometer  scale.  The  time 
taken' for  the  discharge  of  the  electroscope  is  taken  by  means  of 
a  chronometer  or  watch.  By  suitable  lighting,  the  front  edge 
of  the  foil  may  be  made  to  appear  as  a  very  fine  line,  and  its 
position  noted  with  great  precision. 

By  examining  the  diagram  it  will  be  noted  that  the  upper 
condenser  plate  is  connected  with  the  metallic  case.  Detach- 
able metal  cases  are  placed  over  the  condenser  plates  and  over  the 
rod  for  charging  the  electroscope.  Two  of  the  sides  of  the  case 
are  of  glass. 

I  have  here  a  simple  form  of  electroscope  with  leaves  of  alu- 
minum foil,  which  serves  to  show  the  ionization  of  the  air; 
when  the  radium  is  brought  near  the  divergent  leaves  lose  their 
charge  of  negative  electricity  and  rapidly  come  together. 

It  is  of  paramount  importance  that  the  radioactive  substance 
should  be  kept  in  a  room  distant  from  the  electroscope. 

At  the  present  moment  the  clothes  of  every  person  in  this 
room  and  all  the  walls  of  the  room  are  radioactive  by  reason  of  the 
presence  of  the  nine  preparations  of  radium  which  I  have  here 
this  evening. 

Prof.  Curie  told  the  writer  that  it  was  often  impossible  for  him 
to  go  near  his  instruments  to  make  any  measurements  for  hours, 
after  being  in  the  proximity  of  some  radium,  and  those  who 
have  worked  with  this  substance  have  found  the  greatest  diffi- 
culty in  keeping  their  tools  and  instruments  and  themselves  free 
from  the  radioactivity  imparted  by  the  radium.  The  energy 
represented  by  radium  is  something  enormous. 

Elster  and  Geitel*  have  shown  that  a  fine  wire  of  any  metal 
placed  in  the  atmosphere  and  charged  negatively  from  some 
source  of  current,  say  of  500  volts,  causes  the  wire  itself  to 
"become  radioactive,  and  this  radioactivity  may  be  scraped  off 

*  Phys.  Zeit.,  1901,  ii.,  p.  590. 


HAMMER:  RADIUM.  25 

and  will  affect  photograph  plates,  ionize  the  air,  etc.  It 
cannot,  however,  be  washed  off.  It  is  stated  that  light- 
ning rods  and  even  the  leaves  of  trees  all  become  radioactive, 
and  it  has  been  shown  that  falling  rain  and  snow  are  for  a 
time  quite  powerfully  radioactive;  and  after  they  have  fallen,  a 
wire  negatively  electrified  in  the  atmosphere  has  only  a  small 
amount  of  radioactivity,  apparently  showing  that  the  rain  and 
snow  have  carried  the  radioactive  particfes  in  the  atmosphere 
down  to  the  ground. 

McLennan  has  made  experiments  with  the  negatively  charged 
wire  in  Montreal  and  subsequently  at  the  foot  of  Niagara  Falls ; 
and  has  found  the  result  about  one-sixth  as  powerful  in  the  latter 
place  as  in  the  former;  and  he  has  also  shown  that  it  was  not 
necessary  to  electrify  the  wire  used  at  Niagara  Falls,  as  it 
received  a  sufficient  charge  from  the  electricity  in  the  atmosphere. 

McLennan  found  that  rain  caught  in  a  vessel  and  immediately 
evaporated  to  dryness  imparted  radioactivity  to  the  vessel  in 
which  it  was  evaporated. 

Ordinary  water  when  evaporated  and  rain  water  which  has 
stood  for  several  hours  before  being  boiled  down  do  not  yield 
any  radioactivity. 

As  an  evidence  of  radioactivity  imparted  to  another  substance 
by  radium,  I  have  here  some  pieces  of  cardboard  which  consti- 
tuted the  box  which  held  my  samples  of  radium  for  several 
months.  The  box  becoming  injured,  I  broke  it  up,  fortunately 
saving  the  pieces;  and  six  days  after  the  radium  had  been 
removed,  I  looked  up  the  pieces  and  was  surprised  to  find  them 
luminous  in  the  dark.  Subsequently  I  tried  their  effect 
on  a  photograph  plate;  but  did  not  succeed  in  getting  any 
impression.  Three  weeks  later  it  occurred  to  me  to  try  and 
stimulate  the  radioactivity  of  the  cardboard,  which  had  not 
been  near  radium  for  over  a  month,  by  burning  magnesium  wire, 
when  I  found  I  could  make  the  cardboard  brighter  than  it  had 
been  in  the  first  place.  I  have  also  stimulated  the  radioactivity 
by  sparks  from  a  coil,  especially  when  producing  ultra-violet 
rays,  by  using  a  condenser  bridged  across  the  secondary  and 
employing  pure  iron  electrodes.  I  tried  the  burning  magnesium 
with  various  samples  of  cardboard  which  had  not  been  exposed 
to  the  radium,  and  there  was  no  phosphorescence.  It  has  already 
been  stated  that  various  substances  which  become  radioactive 
retain  that  property  for  a  short  time  only,  and  it  is  interesting  to 
note  its  retention  for  such  a  long  period  of  time  and  to  note  this 


26  HAMMER:  RADIUM. 

ability  to  stimulate  and  make  visible  the  imparted  radioactivity. 

This  experiment  suggests  the  discovery  made  by  Prof.  E. 
Wiedemann  that  a  mixture  of  sulphide  of  calcium  with  a  little 
sulphate  of  manganese  is  not  altered  when  exposed  to  cathode 
rays;  but  some  time  after  its  exposure  it  bursts  into  a  vivid 
greenish  glow  when  slightly  heated ;  and  to  this  phenomenon  he 
has  given  the  name  "thermo-luminescence." 

Prof.  S.  P.  Thompson  also  showed  that  fluorspar,  which  by  pro- 
longed heating  has  lost  its  luminescing  power,  regains  the  power 
of  thermo-luminescence  on  exposure  to  Roentgen  rays  when 
reheated. 

Prof.  Trowbridge  also  finds  that  this  restoration  is  also  effected 
by  exposure  to  the  electric  glow  discharge,  but  not  by  exposure 
to  ultra-violet  light. 

It  is  also  stated  that  an  object  coated  with  calcium  sulphide 
and  exposed  to  the  sunlight  will  phosphoresce  about  ten  hours ; 
and  even  after  it  has  lost  its  luminosity,  it  can  be  caused  to  again 
give  light  by  heating  first  by  the  hand,  then  over  a  water  bath, 
and  finally  on  a  hot  stove. 

McLennan  has  found  a  very  large  number  of  salts  are  brought 
into  a  condition  by  cathode  rays,  in  which  warming  makes  them 
radioactive  for  a  short  time,  the  supply  of  negatively  charged 
particles  discharged  from  the  surface  coming  to  an  end. 

Prof.  Rutherford  of  Montreal,  who  has  given  a  great  deal  of 
attention  to  radioactive  substances,  particularly  to  investigations 
into  thorium,  which  next  to  radium  is  the  most  radioactive  sub- 
stance yet  discovered,  has  found  that  by  electrifying  a  wire 
negatively  with  a  current  of  500  volts  connecting  the  positive 
pob  to  the  ground,  and  by  connecting  a  sample  of  thorium  to  the 
earth,  that  the  thorium  particles  were  attracted  to  the  negatively 
charged  wire,  producing  a  greater  radioactivity  than  he  had 
ever  found  in  any  thorium  preparation  which  he  had  made. 

I  have  here  a  sample  of  oxide  of  thorium,  the  radioactivity 
of  which  was  discovered  independently  by  Schmidt  and  Curie. 
This  sample  is  between  98  and  99  per  cent,  purity.  From 
this  body  Prof.  Rutherford  has  isolated  a  substance  which 
he  calls  "ThX;"  and  extraordinary  as  it  may  seem,  it  has 
been  found  after  separation  of  the  active  constituents  repre- 
sented by  the  ThX  from  the  thorium,  that  the  ThX  loses  its  radio- 
activity, and  this  is  taken  up  by  the  thorium  in  exactly  the 
amount  which  the  other  loses. 

Sir  William  Crookes  has  also  separated  a  non-u  ranium  residue 


HAMMER:  RADIUM.  27 

from  uranium,  leaving  the  latter  without  radioactivity.  Whilst 
the  whole  of  the  radioactivity  has  been  concentrated  in  the 
residue  to  which  the  name  UrX  was  given,  Crookes,  as  already 
stated,  claims  that  Actinium  is  but  another  name  for  his  UrX. 

The  only  case  of  radioactivity  induced  by  cathode  rays  in  a 
neutral  substance  has  been  that  of  bismuth,  discovered  by 
Villari. 

Prof.  Curie  has  discovered  that  radioactive  gas  emanates  from 
radium,  and  Rutherford  has  discovered  the  gaseous  emanations 
from  thorium,  Messrs.  Rutherford  and  Soddy  have  investigated 
extensively  these  emanations,  and  they  have  succeeded  in  con- 
densing them  at  the  temperature  of  liquid  air.  A  preliminary 
account  appears  in  the  proceedings  of  the  Chemical  Society  of 
London  for  December,  and  Prof.  Rutherford  writes  me  that  the 
full  paper  will  shortly  appear  in  the  Philosophical  Magazine ;  and 
he  states  furthermore  that  in  his  opinion  this  proves  beyond 
•  doubt  the  gaseous  nature  of  the  emanations. 

The  serious  physiological  effects  of  radium  are  well  known, 
and  Messrs.  Giesel,  Becquerel,  the  Curies  and  others  have  given 
important  evidence  thereof.  As  stated  in  the  appendix  of  a 
paper  read  by  the  writer  at  the  159th  meeting  of  the  INSTITUTE 
on  January  3,  1902,  dealing  with  the  subject  of  radioactivity, 
Prof.  Curie  told  the  writer  that  he  would  not  care  to  trust  himself 
in  a  room  with  a  kilo  of  pure  radium,  as  it  would  burn  all  the 
skin  off  his  body,  destroy  his  eyesight  and  probably  kill  him. 
The  writer  felt  the  effects  for  weeks  of  a  slight  burn  from  in- 
advertently carrying  a  wooden  box  containing  eight  tiny  sealed 
glass  tubes  of  radium  under  his  arm  for  several  hours. 

Mr.  W.  E.  Hidden  has  called  the  attention  of  the  writer  to  some 
phenomena  which  he  has  observed  in  a  mine  in  Barringer's  Hill, 
Llano  County,  Texas,  which  mine  contains  yttrium,  thorium  and 
uranium.  Pockets  of  ore  have  been  found,  ranging  from  a  few 
ounces  up  to  a  capacity  of  70  kilos,  which  were  the  nuclei  or  focal 
points  of  rigid  lines  radiating  in  every  possible  direction.  These 
lines  penetrating  great  masses  of  quartz  and  orthoclase  feldspar, 
and  gigantic  pegmatyte,  to  distance  often  of  several  feet,  in  some 
cases  of  from  five  to  eight  feet,  he  has  observed  that  these  radial 
lines  were  fissures  and  bore  no  relation  to  the  natural  cleavage 
or  the  crystalline  form  of  the  huge  rock  masses  in  which  they 
existed.  Easy  parting  took  place  along  these  radial  lines,  making 
the  ore  quickly  available. 

It  is  Mr.  Hidden's  theory  that,  as  these  lines  directed  to  ores 


28  HAMMER:  RADIUM. 

rich  in  uranium  and  thorium,  both  well  known  sources  of  radium, 
etc.,  the  phenomenon  is  due  to  an  electric  or  other  effect  of  radio- 
activity; it  being  untenable,  he  believes,  to  explain  this  phe- 
nomenon on  the  basis  of  expansion  or  contraction. 

The  slide  which  I  will  show  on  the  screen  shows  clearly  a  pocket 
of  ore  with  the  lines  radiating  therefrom  in  all  directions. 

Eighteen  years  ago,  while  in  Italy,  the  author  visited  the 
celebrated  aquarium  in  Naples,  which  is  probaby  the  finest  in  the 
world ;  and  while  there  was  enabled  to  test  the  shocking  abilities 
of  the  Electric  Ray,  or  "Torpedo  Galvani,"  and  was  astonished 
at  the  tremendous  shock  which  he  received;  and  in  this  connec- 
tion, it  is  interesting  to  call  attention  to  the  fact  that  there  are 
fifty  or  more  fishes  which  are  known  to  possess  this  property  of 
giving  powerful  shocks.  The  "Gymnotus"  or  Electric  Eel,  and 
the  "Torpedo  Galvani"  or  Electric  Ray  being  the  best  known 
of  these. 

It  will  be  recollected  that  Faraday  drew  a  powerful  spark  from 
a  Gymnotus  at  the  Polytechnicum,  London,  and  he  estimated 
the  shock  to  be  equivalent  to  that  given  by  a  battery  of  Leyden 
jars  of  3,500  square  inches  of  surface.  And  many  writers  have  re- 
ferred to  the  ability  of  these  electric  fishes  to  give  powerful  shock 
for  a  long  period  of  time.  D'Arsonval  has  caused  them  to  light 
incandescent  lamps  and  they  have  been  known  to  magnetize 
needles  and  decompose  water  by  the  electricity  they  produce. 
These  fishes  doubtless  using  this  faculty  as  a  means  of  defence 
and  also  for  procuring  food.  My  object  in  mentioning  this  is  to 
state  that  last  Fall  I  again  visited  Naples  and  thinking  that 
perhaps  an  electric  torpedo  was  on  exhibition,  it  occurred  to  me 
to  take  with  me  some  half  dozen  tubes  of  radium  which  I  had  in 
my  bag,  and  see  whether  the  radium  had  any  effect  upon  the 
power  of  the  fish  to  give  powerful  shocks.  The  fish,  as  at  the 
time  of  my  previous  visit,  was  lying  in  a  shallow  wooden  box 
containing  wet  sand  and  a  small  amount  of  water.  By  taking 
hold  of  the  side  of  the  fish  and  pressing  with  the  thumb  on  one 
side  and  the  fingers  on  the  other,  or  by  either  pinching  or  tap- 
ping the  fish,  the  cells  with  which  the  fish  was  equipped  dis- 
charged themselves  and  gave  a  shock  sufficient  to  twist  one's 
arm  very  badly.  After  the  members  of  our  party  had  each 
received  a  shock,  and  as  soon  as  a  few  persons  present  had  gone 
away,  I  laid  the  six  tubes  of  radium  on  the  fish  (which  is  shaped 
very  much  like  a  flounder),  leaving  them  there  for  about  twenty 
minutes.  I  then  replaced  the  tubes  in  the  box,  and  taking  hold 


HAMMER:  RADIUM.  2£ 

of  the  fish  tried  for  fifteen  minutes  to  get  it  to  give  me  a  shock  by 
tapping  or  pinching  in  the  same  manner  as  previously  done  when, 
the  fish  gave  off  shocks,  and  without  receiving  the  slightest  shock. 
Now,  I  am  prepared  to  admit  that  the  fish  might  have  been  "en- 
tirely out  of  shocks  ";  still,  it  is  well  known  that  these  fishes  will 
continue  to  give  out  shocks  for  a  very  long  period  of  time,  one 
authority  reporting  360  shocks  in  seven  minutes'  time;  but  after 
exposing  the  fish  to  the  radium,  I  could  get  absolutely  no  mani- 
festation ;  and  in  this  connection,  it  is  to  be  remembered  that  the 
physiological  effects  of  radium,  such  as  burning,  destroying 
microbic  life,  producing  the  sensation  of  light  when  a  tube  is  held 
against  the  closed  eye  or  temples  (which  is  doubtless  largely  due 
to  the  phosphorescence  of  the  pupil  of  the  eye,  but  which  may 
also  affect  the  nerve  centers),  and  also  the  electrical  effects,  where 
charged  bodies  are  caused  to  give  off  their  charge  by  the  ioniza- 
tion  of  the  air ;  and  one  must  also  remember  the  very  numerous 
•  chemical  effects  and  the  destruction  of  the  germinating  power  of 
seeds,  the  changing  of  oxygen  into  ozone,  and  various  other 
phenomena  of  radium  which  would  lead  one  to  wonder  whether 
the  radium  did  not  affect  the  ability  of  the  fish  to  give  off 
electric  shocks,  perhaps  producing  a  partial  paralysis. 

The  experiment  is  of  some  interest,  and  may  be  perhaps 
repeated  by  others  who  have  better  facilities  than  I  to  continue 
the  investigation.  I  have  sometimes  wondered  how  that  fish 
was  getting  along  in  Naples ;  though  I  believe  the  waters  of  the 
Mediterranean  abound  in  them. 

Note — Since  writing  the  above  description  of  his  own  experi- 
ments, the  writer  has  learned  of  the  recent  experiments  conducted 
by  Prof.  Curie,  in  which  a  few  milligrams  of  radium  introduced  be- 
neath the  skin  of  a  mouse  near  the  vertebral  column  produced 
death  by  paralysis  in  three  hours;  and  tubes  of  radium  placed 
in  contact  with  the  back  of  the  necks  of  guinea  pigs  have  killed 
or  paralyzed  these  animals  in  a  few  hours,  according  to  the 
length  of  exposure  to  its  fatal  radiations. 

As  illustrating  the  action  of  radium  rays  upon  bacteria,  E. 
Aschkinass  and  W.  Caspari  speak  of  exposing  cultures  of  Micro- 
coccus  prodigiosus  to  a  radium  preparation,  and  state  that  the 
rays  killed  the  germs  very  effectively  in  about  three  hours. 

The  work  of  Rutherford,  the  Curies,  Becquerel,  and  others  has 
demonstrated  that  there  are  three  entirely  distinct  types  of  rays, 
emanating  from  radium  (Rutherford  having  first  pointed  out 
that  uranium  possessed  two  separate  types  of  rays,  "a"  and  "/?  '" 


30  HAMMER:  RADIUM. 

the  former  easily  absorbed  even  by  gases,  whilst  the  latter  are  very 
penetrating  and  but  little  absorbed  by  gas).  Those  which  con- 
stitute by  far  the  most  important  class  are  the  "  a  "  rays.  They 
constitute  the  major  proportion  of  the  rays,  and  are  those  which 
produce  the  greatest  portion  of  the  ionization  of  the  gas,  which 
has  been  observed  under  experimental  conditions. 

These  "a"  rays  possess  in  common  certain  characteristics  of 
Roentgen  rays,  and  by  many  have  been  thought  to  be  Roentgen 
rays.  I  shall  call  your  attention  later  to  certain  effects  which 
are  identical  with  those  produced  by  Roentgen  or  X-rays.  They 
have  been  considered  absolutely  non-de viable,  as  X-rays  have 
been  held  to  be. 

Rutherford  has,  however,  recently  shown  that  in  a  very 
powerful  magnetic  field  he  could  deflect  about  30  per  cent,  of  the 
rays,  and  in  experiments  now  being  conducted  with  a  strong 
electric  field,  he  has  been  able  to  deflect  about  45  per  cent,  of  the 
"a"  rays.  The  "a"  rays  are  readily  absorbed,  and  a  thin 
screen  of  metal  will  serve  to  cut  off  the  greater  portion  of 
them. 

In  this  connection  I  would  state  that  Mr.  Tesla  informed  the 
writer  recently  of  an  experiment  he  had  made  in  which  he  had 
succeeded  in  deflecting  the  X-rays  themselves,  and  M.  Blondelot 
has  recently  claimed  as  the  result  of  his  experiments  that  X-rays 
are  susceptible  of  polarization.  If  this  is  so,  it  is  argued  they 
may  be  shown  to  be  ordinary  light  waves  of  extremely  short 
wave  length. 

Strutt  and  Crookes  have  suggested  that  the  "a"  rays  consist 
of  positively  electrified  particles,  and  this  view  Rutherford  sup- 
ports, calling  attention  to  the  fact  that  they  possess  character- 
istics similar  to  the  "Canal  Strahlen"  of  Goldstein.  These 
Goldstein  rays  have  been  shown  by  Wien  to  be  positively  charged 
particles,  moving  at  high  velocities. 

Rutherford,  as  a  result  of  his  most  recent  observations,  con- 
siders that  the  "a"  rays  move  at  much  higher  velocity  than  the 
Goldstein  rays;  and  he  estimates  that  the  energy  of  the  "a" 
rays  is  a  thousand  times  greater  than  that  of  the  "ft"  rays. 

Rutherford  says  all  the  radioactive  substances,  including 
polonium,  as  well  as  excited  bodies  and  the  emanations,  give  out 
"a"  rays. 

The  "ft"  rays  are  much  more  penetrative  and  much  longer, 
and  in  every  particular  correspond  to  the  characteristics  of 
cathode  rays.  They  are  readily  deflected  by  a  magnet.  They 


HAMMER:  RADIUM.  31 

discharge  electrified  bodies  by  ionization  of  the  air,  affect  photo- 
graph plates,  etc. 

M.  Villard,  in  1899,  proved  that  the  cathode  rays  are  negatively 
electrified  corpuscles  or  fragments  of  atomic  hydrogen,  and  these 
corpuscles,  as  they  were  named  by  J.  J.  Thomson,  which  he  has 
shown  to  be  one  one-thousandth  of  the  mass  of  the  hydrogen 
atom,  are  projected  from  the  cathode  at  a  speed  approximating 
70,000  miles  per  second. 

The  "f"  rays  are  the  rays  possessing  the  greatest  penetrative 
effect.  They  will  excite  or  produce  radioactivity  through  the 
air  at  a  distance  of  three  or  four  feet  or  more. 

Some  recent  experiments  made  by  Rutherford  show  the 
relative  penetration  of  the  three  classes  of  rays  through  aluminum 
sheets  of  varying  thicknesses,  before  a  loss  is  observed  of  half  of 
the  intensity,  and  this  shows  for  the 

"a"  rays  a  thickness  of  aluminum  of  .0005  cm. 

"  /?"  rays  a  thickness  of  aluminum  of      .05  cm. 

"?-"  rays  a  thickness  of  aluminum  of        8.  cm. 

Mr.  Rutherford,  who  has  conducted  most  painstaking  investi- 
gations into  the  penetrative  character  of  the  radiations  from 
uranium,  radium,  thorium,  etc.,  recently  wrote  the  author  in 
answer  to  some  questions  on  the  subject,  that  he  had  found  that 
the  radium  rays  were  reduced  to  half  value  after  passing  through 
1  cm.  of  lead,  1  inch  of  iron  and  about  8  inches  of  water,  the 
radiation  being  reduced  to  about  1  per  cent,  of  its  original  value, 
after  passing  through  7  cm.  of  lead,  7  inches  of  iron  and  56  inches 
of  water. 

In  the  lantern  slide  thrown  on  the  screen  is  an  interesting 
illustration  of  the  effect  of  magnetism  on  the  deflectable  rays 
from  radium.  There  are  four  large  steel  magnets,  two  being 
placed  opposed  to  each  other,  and  the  other  two  so  that  unlike 
poles  are  opposite  to  each  other,  making  a  strong  field  of  force 
between  the  two  magnets.  I  have  placed  six  tubes  of  radium  a 
short  distance  above  the  magnets  and  in  a  line  running  across 
and  between  the  poles  of  the  two  pairs  of  magnets.  It  will  be 
seen  that  the  magnetic  rays  in  the  case  of  one  pair  of  magnets 
have  repelled  the  radium  rays  so  that  the  negative  is  but 
slightly  affected.  Whereas,  in  the  case  of  the  other  pair  of 
magnets  the  radium  rays  have  been  attracted  by  the  magnets 
affecting  considerably  the  negative  around  the  pole  pieces. 

Prof.  Curie  states  that  half  of  the  induced  radioactivity,  when 
exposed  to  the  air,  is  lost  in  certain  substances  in  half  an  hour; 


32  HAMMER:  RADIUM. 

but  in  a  closed  vessel,  where  the  air  has  been  made  radioactive, 
however,  this  radioactivity  has  not  lost  half  of  its  strength,  even 
after  four  days'  time. 

It  is  desirable  to  keep  radium  free  from  moisture,  preferably 
in  sealed  glass  tubes.  It  readily  takes  up  moisture,  and  then 
soon  loses  its  luminosity,  which  may,  however,  be  regained  by 
dissolving  and  precipitating  the  substance  and  thoroughly  drying 
it.  The  luminosity  may  also  be  considerably  heightened  by 
subjecting  the  radium  to  high  temperatures. 

Polonium  like  uranium  does  not  possess  the  power  of  exciting 
radioactivity,  as  it  does  not  give  off  any  emanations ;  whereas,  in 
the  case  of  radium  and  thorium,  there  is  an  actual  emanation, 
producing  radioactivity  in  surrounding  objects  by  the  deposit  of 
radioactive  matter. 

When  one  considers  the  remarkable  effects  produced  by  radium 
it  would  almost  seem  that  it  is  matter  tearing  itself  into  tiny 
pieces,  and  projecting  these  infmitesimally  small  particles 
through  all  matter  at  a  speed  from  half  to  even  the  full  speed  of 
light,  and  rendering  all  substances  about  it  radioactive,  and  still 
without  appreciable  loss  in  weight  in  the  original  substance,  and 
without  disparagement  of  the  accepted  wave  theory  of  light  one 
naturally  "harks  back"  to  Newton's  corpuscular  theory  of 
light. 

While  various  theories  have  been  advanced  to  account  for  the 
phenomena  of  radium,  there  remain  many  things  which  have  not 
been  satisfactorily  accounted  for;  and  perhaps  the  subject  which 
has  been  most  widely  discussed  is  the  loss  in  weight  of  radio- 
active substances. 

At  the  British  Association  meeting  last  summer,  Prof.  J.  J. 
Thomson  is  reported  to  have  stated  that  if  a  square  centimeter 
of  surface  were  covered  with  pure  radium,  it  would  only  lose  in 
weight  one  thousandth  of  a  milligram  in  a  million  years.  This  is- 
in  accordance  with  the  previous  statements  made  by  Becquerel. 

Later  in  the  year,  A.  Heydweiller,  of  the  Royal  University, 
Munster,  Germany,  stated  that  he  had  been  testing  a  sample  of 
De  Haen's  preparation  of  radium,  and  found  that  it  lost  in  weight 
two  one-hundredths  of  a  milligram  per  day  for  fifty  days,  and  a 
whole  milligram  in  that  period.  (Phys.  Zeit.,  Oct.  15,  1902.) 

The  great  discrepancy  in  the  statements  on  this  important 
subject  led  the  writer  to  enter  into  correspondence  with  Profs. 
J.  J.  Thomson,  Henri  Becquerel,  Lord  Kelvin,  Sir  William 
Crookes,  P.  Curie  and  A.  Heydweiller,  which  resulted  in  the  fol- 
lowing expression  of  view. 


HAMMER:  RADIUM.  33 

Prof.  Thomson  was  inclined  to  think  that  from  the  magnitude 
of  loss  found  by  Heydweiller,  it  must  be  due  to  some  secondary 
effect,  and  he  stated  that  he  could  not  speak  with  certainty 
without  a  greater  knowledge  of  the  details  of  the  experiments- 
As  accounting  for  the  results  he,  however,  drew  attention  to  the 
well-known  coloration  of  glass  by  radium,  by  remarking,  "One 
point,  however,  that  ought  to  be  attended  to  in  these  experi- 
ments is  the  effect  of  the  radiation  from  radium  on  glass.  Glass, 
as  is  well  known,  gets  deeply  colored  when  in  contact  with 
radium.  It  seems  to  me  possible  that  the  glass  might  be  charged 
right  through.  If  this  were  the  case,  it  is  possible  that  reactions 
might  occur  between  the  glass  and  the  air,  producing  volatile 
substances  and  a  loss  of  weight.  I  only  throw  this  out  with 
hesitation,  for  as  I  said  before,  I  am  not  familiar  with  the  details 
of  the  experiments. " 

Prof.  Becquerel  informed  the  writer  that  he  knew  nothing 
•reliable  regarding  the  experiments  of  Heydweiller,  and  called 
attention  to  his  original  paper  on  this  subject  which  appeared 
in  the  Comptes  rendus  of  March  26,  1900,  adding,  "I  believe 
I  am  the  first  to  have  published  an  estimate  in  this  way  which 
could  only  result  from  my  own  experiments.  The  loss  of  one 
milligram  per  square  centimeter  requires  one  thousand  million 
years.  This  statement  refers  only  to  the  part  of  the  de viable 
portion  of  the  radiation  to  which  measurements  were  applied; 
but  this  is  only  a  part  of  the  total  loss.  The  de  viable  radiations 
comprise  rays  ranging  from  109  and  3.1010  c.m.  Besides,  there  is 
also  all  the  non-deviable  portion,  either  penetrating  or  absorbing, 
which  corresponds  to  a  notable  loss  of  energy;  and  in  addition, 
if  the  emanation  is  of  material  importance,  which  seems  quite 
probable,  the  loss  on  this  account  would  be  a  thousand  times 
greater.  These  estimates  are  but  theoretical,  for  it  is  probable 
that  at  least  a  portion  of  the  mass  calculated  or  estimated  as 
material  is  apparent  and  corresponds  to  the  effects  of  induction. " 

In  response  to  an  expression  of  view  from  Sir  William  Crookes 
on  a  theory  to  satisfactorily  account  for  the  phenomena  of  radio- 
active substances,  he  wrote  as  follows:  "You  will  find  them 
fully  given  in  my  address  to  the  British  Association  at  their 
Bristol  meeting  in  1898.  I  have  not  seen  any  special  reason  to 
alter  the  views  there  propounded";  and  in  writing  on  the  sub- 
ject of  Heydweiller's  experiments,  Prof.  Crookes  says,  "I  do  not 
think  the  experiments  of  Heydweiller  have  been  corroborated 
by  other  observers;  and  there  are  many  sources  of  error  in  his 


34  HAMMER:  RADIUM. 

experiments  which  I  should  like  to  see  discussed  before  giving 
credence  to  it.  Personally,  I  find  no  loss  of  weight  in  a  rich 
sample  of  radium  compound  during  continuous  weighings  ex- 
tending over  many  months.  I  should  be  inclined  to  agree  with 
Becquerel  and  J.  J.  Thomson." 

Lord  Kelvin  wrote  that  he  was  sorry  not  to  have  been  able  to 
make  any  experiments  on  radioactive  substances  which  could 
allow  him  to  offer  any  opinion  that  would  be  helpful  on  the 
subject,  and  added,  "What  you  tell  me  regarding  radium  and 
your  correspondence  with  Prof.  J.  J.  Thomson  is  very  interesting. 

On  this  point  Prof.  Curie  recently  wrote  me  as  follows :  "I 
never  did  believe  in  the  exactness  of  Mr.  Heydweiller's  experi- 
ments; and  I  always  thought  he  did  not  take  care  enough  to 
avoid  some  source  of  errors.  In  fact,  with  a  substance  consider- 
ably stronger  than  his  own  I  only  obtained  a  reduction  in  weight 
of  1-10  of  a  milligram  in  four  months  for  several  decigrams  of 
substance,  and  as  the  tubes  were  used  at  the  same  time  in  sev- 
eral experiments,  that  loss  of  weight  does  not  allow  me  to  affirm 
that  radium  is  losing  weight  spontaneously.  I  believe,  mean- 
while, as  does  Mr.  Heydweiller,  that  the  question  cannot  be  an- 
swered in  any  other  than  an  experimental  way,  and  that  all 
speculative  theories  are  of  small  interest.  I  have  published  my 
recent  researches  in  the  Comptes  Rendus  de  VAcademie  des  Sci- 
ences de  Paris." 

As  regards  the  published  statements  of  Prof.  Heydweiller's 
experiments,  the  writer  can  state  that  he  is  most  reliably  informed 
that  a  mishap  occurred  during  his  experiments  which  resulted  in 
one  of  the  tubes  becoming  cracked,  which  was  not  observed  until 
later;  and  that  this  practically  nullified  the  results  published; 
and,  in  fact,  they  have  not  been  confirmed  by  subsequent  tests; 
but,  on  the  other  hand,  they  tend  to  corroborate  the  experiments 
of  Becquerel  and  the  statements  made  by  him,  Sir  William 
Crookes,  J.  J.  Thomson  and  others.  The  writer  is  also  informed 
that  Prof.  Heydweiller  is  continuing  further  experiments,  the 
results  of  which  will  doubtless  be  published  when  his  investiga- 
tions are  complete. 

As  bearing  upon  the  coloration  of  glass  already  referred  to,  I 
hold  in  my  hand  a  flask  which  I  secured  at  the  laboratory  in  Paris 
which  has  contained  radium,  and  has  been  most  beautifully 
colored  a  deep  violet.  I  also  have  several  tubes  in  which  radium 
has  been  kept,  which  are  similarly  colored,  and  in  this  connection 
I  would  call  attention  to  the  fact  that  X-ray  tubes  which  have 


HAMMER:  RADIUM.  35 

been  in  use  for  a  considerable  time  become  similarly  colored, 
forming  another  link  between  the  Roentgen  rays  and  radium 
rays. 

I  also  have  here  a  tiny  bulb  of  glass  which  is  colored  a  deep 
brown.  I  have  seen  only  one  other  piece  of  glass  colored  in  this 
way,  this  being  due  to  the  difference  in  the  chemical  constituents 
of  the  glass  (though  in  some  cases  the  glass  subsequently  turns  a 
violet  color).  This  is  a  duplicate  of  the  tiny  tube  which  Prof. 
Curie  showed  the  writer,  which  contained  between  two  and  three 
one-hundredths  of  a  gramme  of  chemically  pure  radium. 


FIG.  6. — Radiograph  Made  by  Radium  of  a  Disk  for  Testing 
Radioactivity,  a  Block  of  Rock-salt  and  a  Lump  of  Pitch- 
blende. 


It  is  interesting  to  note  that  the  Becquerel  rays  induce  activity 
which  persists,  whereas  that  excited  by  Roentgen  rays  ceases 
immediately  on  the  removal  of  the  rays. 

As  illustrating  the  X-ray  character  of  radium  rays  I  would 
call  your  attention  to  Fig.  6,  in  the  center  of  which  is  shown  a 
block  of  rock  salt.  The  original  sample  was  about  one  inch 
thick,  and  was  so  transparent  that  a  person's  features  might  be 
seen  through  it.  The  rock  salt  is  not  only  transparent  to  ordin- 
ary light,  but  also  to  ultra-violet  light,  whereas  it  is  very  opaque 
to  X-rays. 


36  HAMMER:  RADIUM. 

Mrs.  Hammer,  appreciating  the  serious  physiological  effects  of 
radium,  has  made  the  interesting  suggestion  that  radium  be 
kept  in' boxes  made  of  rock  salt;  and  the  author  is  now  having 
such  a  receptacle  made.  This  might  be  even  more  satisfactory 
than  a  lead  box.  It  would  be  interesting  to  note  the  change  -in 
the  temperature  of  such  a  box  or  vial  which  so  well  intercepts 
the  Radium  rays. 

The  illustration  referred  to  was  made  by  placing  the  rock  salt 
on  a  photograph  plate  with  the  radium  some  5  inches  above  it. 

To  the  right  of  the  rock  salt  is  shown  a  piece  of  uraninite  (pitch- 
blende), from  which  radium  is  extracted;  and  you  will  note  that 
not  only  has  the  mineral  been  photographed  by  the  radium  above 
it,  but  the  radium  has  acted  on  the  radioactive  constituents  of 
the  pitchblende  and  caused  this  to  affect  the  plate. 

The  disk  shown  at  the  left  of  the  cut  is  one  made  in  Paris  for 
the  examination  of  radioactive  substances.  I  have  one  of  these 
here,  and  it  consists  of  a  rim  of  brass,  enclosing  a  brass  washer 
with  a  glass  disk  at  the  center.  The  opposite  face  is  covered  with 
aluminum  foil,  and  between  the  aluminum  and  the  glass  is  placed 
some  radium  of  1,000  radioactivity.  Substances  which  it  is 
desired  to  examine  are  laid  on  this  disk.  It  is,  however,  a  rather 
crude  piece  of  apparatus;  but  in  the  cut  shown  not  only  has  the 
disk  been  photographed  by  the  radium  5  inches  above  it,  but  the 
radium  inside  of  the  disk  has  penetrated  through  the  aluminum 
and  fogged  the  plate. 

In  Fig.  7  are  shown  some  interesting  effects  of  the  radium 
rays  in  affecting  a  photograph  negative  after  passing  through 
lenses.  The  lenses  "A"  and  "B"  are  plano-convex  condensing 
lenses,  one  being  placed  with  the  flat  surface  down,  and  the 
other  with  the  convex  surface  down.  "C"  is  a  double  convex 
lens  of  crystal,  "  D  "  is  a  plano-convex  lens  of  uranium  glass  and 
"E"  represents  an  ordinary  glass  prism. 

It  is  stated  that  radium  rays  cannot  be  reflected,  refracted  or 
polarized.  Those  familiar  with  the  phenomena  of  light  will,  I 
feel  sure,  be  interested  in  the  above  photograph. 

In  Fig.  8  is  shown  another  illustration  of  the  penetrative  char- 
acter of  the  rays,  it  being  a  thick  lead  box  containing  six  tubes  of 
radium,  ranging  from  a  radioactivity  of  40  to  7,000;  this  box 
being  laid  upon  a  large  steel  magnet  f  of  an  inch  thick.  You  will 
note  the  degree  of  penetration  of  both  the  lead  and  the  steel 
varies  according  to  the  radioactivity  of  the  radium  in  the  various 
tubes.  The  exposure  was  made  in  twenty-two  hours. 


HAMMER:  RADIUM. 


87 


pIG    7 — Radiographs  of  Various  Types  of  Lenses  Made  by  Radium. 


FIG.  8.— Radiograph  showing  Degrees  of  Penetration  of 

a  thick  sheet  of  Lead  and  a  Steel  Magnet  by  Tubes 

of  Radium  of   Different  Radioactivities 


38  HAMMER:  RADIUM. 

Fig.  9  illustrates  the  penetration  of  the  rays  through  black 
paper,  the  steel  tool  shown  having  been  laid  on  the  plate  covered 
with  two  thicknesses  of  heavy  black  paper,  such  as  used  for 


FIG.  9. — Radiograph  of  Steel  Tool   Made  by   Radium  Acting 
Through  Two  Thick  X-ray  Plate  Envelopes. 

wrapping  X-ray  plates;    a  single  sheet  of  which  is  entirely  im- 
pervious to  light.     The  exposure  was  made  in  twenty-four  hours. 
Fig.  10  shows  a  mouse  which  was  radiographed  in  twenty-four 
hours  by  laying  it  directly  on  a  plate,  which  was,  as  in  the  case  of 


FIG.   10. — Radiograph  of  a  Mouse  Made  by  Radium  in  Twenty- 
four  Hours 


other  experiments,  placed  in  the  bottom  of  a  trunk,  the  trays 
being  replaced  and  the  trunk  wrapped  in  three  thick  rugs,  and 
kept  in  a  dark  room  for  twenty-four  hours. 

The  radiograph  of  the  mouse  shown  in  Fig.  11  represents  a 
mouse  caught  on  another  occasion,  in  which  I  placed  the  mouse, 
trap  and  all  on  the  plate,  leaving  it  there  for  three  days.  The 
trap  was  an  ordinary  6  cent  trap ;  and  it  will  be  noted  that  the 
metal  parts  of  the  trap  are  shown  opaque,  whereas  the  portion  of 
the  wood  nearest  to  the  radium  is  shown  absolutely  transparent, 
as  if  it  had  been  exposed  to  X-rays.  In  the  original  photograph 


HAMMER:  RADIUM. 


39 


the    mouse    is    also    shown    somewhat    transparent,    indicating 
slightly  the  bones. 

I  also  show  you  in  Fig.  12  and  upon  the  screen  a  slide  which  I 
have  made  of  a  radiograph  of  a  human  hand.  This  was  exposed 
for  eight  days,  and  bears  resemblance  to  an  X-ray  picture  which 
has  been  overexposed.  In  making  a  faint  print  of  this,  a  slight 
trace  of  the  bone  is  shown  and  the  embalming  material  em- 
ployed is  brought  out  strongly.  This  is,  perhaps,  the  first  pic- 
ture made  of  the  human  hand  by  means  of  radium;  and  it 
would  not  have  been  possible,  of  course,  to  have  exposed  a  living 
person  to  these  rays  for  even  a  small  percentage  of  this  length 


FIG.  11. — Radiograph  of  Mouse  Caught  in  Trap  and  Exposed  to 
Tube  of  Radium  for  Three  Days.  (Note  Transparency  of 
Wood,  as  with  X-rays.) 

of  time.  Perhaps  subsequent  experiments  will  bring  out  much 
more  strongly  the  bone  structure  (the  irregularity  in  the  fingers 
is  due  to  their  being  somewhat  cramped). 

As  X-rays  will  excite  phosphorescence  in  many  substances,  one 
would  naturally  wonder  whether  there  were  any  X-ray  charac- 
teristics in  phosphorescent  substances. 

An  interesting  experiment  is  shown  in  Figs.  13  and  14.  In  the 
former  experiment,  I  have  placed  strips  of  various  metals,  such  as 
brass,  iron,  copper,  tin,  lead,  tinfoil,  aluminum, platinum, magne- 
sium, etc.  and  strips  of  carbon,  vulcanite,  glass,  mica  and  celluloid. 


40 


HAMMER:  RADIUM. 


FIG.   12. — Radiograph  of  a  human  hand  made  by  Radium  in  8  days'  time. 


FIG.  13. — Photograph  Made  by  Phosphorescent  Sulphide  of 
Calcium  of  Iron,  Brass,  Copper,  Tin,  Lead,  Aluminum,  Pla- 
tinum, Tinfoil,  Magnesium,  Carbon,  Glass,  Mica,  Celluloid, 
Vulcanite,  etc..  and  Strip  of  Black  Paper.  (See  Fig.  14.) 


HAMMER:  RADIUM.  41 

Across  the  middle  of  the  plate  I  have  placed  a  strip  of  thick  black 
paper  cut  from  an  X-ray  plate  envelope.  I  then  sprinkled  over  the 
entire  plate  by  means  of  a  sieve  sulphide  of  calcium,  which  I  had 
made  brilliantly  phosphorescent  by  exposure  to  burning  mag- 
nesium ribbon.  The  only  substances  which  allowed  the  light  to 
pass  through  at  all  were  the  glass,  mica  and  celluloid,  the  other 
substances,  including  the  paper,  being  very  opaque,  showing 
apparently  only  the  presence  of  ordinary  light  rays.  This  plate 
was  placed  for  twenty-four  hours  in  a  dark  room. 


FIG.  14. — Radiograph  Made  by  Radium  of  Same  Substances  as 
in  Fig.  9.  Note  Black  Paper  is  Transparent,  as  are  Certain 
of  the  Other  Substances,  especially  those  directly  below  the 
Radium. 

In  Fig.  14  are  shown  some  substances  similarly  arranged,  but 
exposed  to  a  tiny  tube  of  radium  of  7,000  radioactivity,  which 
was  placed  3  inches  above  the  plate  and  near  the  center.  The 
exposure  was  made  for  twenty-five  hours;  and  it  will  be  noted 
that  the  strip  of  black  paper  has  entirely  disappeared,  and  the 
various  substances  underneath  it  have  been  penetrated  to  a 
greater  or  less  degree;  particularly,  those  nearest  to  the  radium. 

A  bibliography  of  " Radio- Activity,"  even  at  this  early  date, 


42  HAMMER:  SELENIUM. 

would  be  very  extensive ;  among  the  publications  containing  the 
most  important  contributions  are  The  Phil.  Mag.,  Comptes  Ren- 
dus,  Ann.  der  Physik,  Revue  Gen.  des  Sciences,  Nature,  Jour,  de 
Phys.,  Soc.  Francaise,  Phys.  Bulletin,  Chem.  News,  Phys.  Ges. 
Verk.,  Phys.  Zeit,  Science  Abstracts,  Wied.  Ann.,  Proc.  Royal 
Soc.,  etc. 

THE  PROPERTIES  AND  APPLICATIONS  OF  SELENIUM. 
The  extraordinary  property  which  selenium  possesses  of  vary- 
ing its  electrical  resistance  on  exposure  to  light  is  a  phenomenon 
which  has  been  known  for  a  long  time ;  but  the  commercial  appli- 
cations of  this  peculiar  property  possessed  by  selenium  have  not 
been  properly  appreciated  up  to  the  present  time. 

It  is  my  purpose  to  invite  your  attention  this  evening  to  a 
number  of  applications  of  selenium  which  the  writer  believes  will 
prove  of  no  small  interest  to  the  electrical  engineering  profession 
and  perhaps  stimulate  investigations  in  this  most  promising  field . 
The  Swedish  scientist,  Berzelius,  discovered  selenium  in  1817, 
as  a  by-product  from  the  distillation  of  sulphuric  acid  from  iron 
pyrites.  The  proximity  of  the  earth  and  moon  suggested  to 
Berzelius  the  name  "Selenium"  after  the  Greek  "selene" 
(moon) ;  this  being  the  result  also  of  the  striking  similarity  of  the 
properties  of  selenium  with  those  of  tellurium,  which  is  a  term 
derived  from  the  Latin  "Tellus,"  (earth).  Its  atomic  .weight  is 
79.5;  specific  gravity  when  crystallized,  4.788;  its  observed 
vapor  specific  gravity  at  2588°  F.  5.68.  It  is  a  non-metallic 
element,  which  possesses  characteristics  similar  to  phosphorus, 
sulphur  and  tellurium.  When  melted  at  212°  Centigrade  and 
allowed  to  cool  rapidly,  it  forms  a  brown  amorphous  mass  of 
conchoidal  fracture.  In  this  condition  it  is  a  high  class  insulator. 
It  has  been  said  that  a  small  piece  of  it  would  represent  the  resist- 
ance of  a  wire  stretched  from  the  earth  to  the  sun.  When  heated 
for  quite  a  time  at  a  temperature  of  100°  Centigrade,  selenium 
becomes  a  conductor  of  electricity  to  a  limited  degree,  this 
increasing  with  an  increase  of  current  and  varying  according  to 
the  direction.  Selenium  has  neither  taste  nor  smell. 

The  red  vapor  rising  from  selenium  when  subject  to  intense 
heat  is  exceedingly  poisonous,  and  care  should  therefore  be  taken 
when  experimenting  with  selenium  in  liquid  form. 

Selenium  is  usually  supplied  commercially  in  a  vitreous  form. 
Here  are  some  samples  of  it,  and  you  will  note  that  it  is  as 
structureless  as  glass  and  resembles  black  sealing  wax.  I  also 


HAMMER:  SELEXIUM.  43 

have  here  some  amorphous  selenium  in  which  form  it  is  a  finely 
divided  brick  red  powder.  This  changes  into  vitreous  selenium 
when  exposed-  to  a  temperature  of  from  80°  to  100°  Centigrade. 
In  order  to  obtain  crystalline  selenium,  in  which  form  it  is  useful 
for  selenium  cells,  it  must  be  kept  as  already  stated  at  from  100° 
to  200°  Centigrade  for  some  time,  the  black  mass  being  changed 
into  a  hard  slate-colored  metallic  looking  substance.  .In  this 
form  even  the  thinnest  films  are  opaque  to  light,  whereas  in  the 
vitreous  form  the  film  would  be  transparent  and  ruby  red  in 
color.  I  have  some  of  these  films  here  for  your  examination. 

Selenium  is  to-day  employed  to  a  considerable  extent  for  the 
coloration  of  glass. 

In  1851  Hittorf  first  discovered  the  effects  of  temperature  on 
selenium;  but  it  was  not  until  February  12,  1873,  that  Mr. 
Willoughby  Smith  sent  a  communication  to  President  Latimer 
Clark,  of  the  Society  of  Telegraph  Engineers  of  London,  calling 
attention  to  the  effect  of  light  in  reducing  the  resistance  of 
selenium.  An  assistant  of  Mr.  Willoughby  Smith,  a  Mr.  May, 
who  was  a  telegraph  clerk  at  Valencia,  called  attention  to  the 
fact  that  some  pencils  of  selenium  which  had  been  used  to  give 
a  high  resistance  in  connection  with  some  of  the  cable  testing 
work  conducted  by  Mr.  Willotfghby  Smith,  showed  a  marked 
change  in  resistance  when  the  sliding  cover  of  the  box  which  held 
the  selenium  was  removed,  and  the  selenium  was  exposed  to 
sunlight.  These  selenium  pencils  varied  in  length  from  5  to  10 
centimeters,  and  were  1  to  1£  mm.  in  diameter;  they  were  her- 
metically sealed  in  glass  tubes  with  connecting  wires  of  platinum 
at  each  end.  Little  credence  was  given  to  the  original  announce- 
ment; and  it  was  only  after  Earl  Ross  verified  this  statement, 
and  proved  that  the  action  was  due  solely  to  light,  and  showed 
the  effects  of  the  light  of  different  portions  of  the  spectrum, 
that  it  met  with  serious  consideration.  Since  that  time  n  v.ch 
work  has  been  done  investigating  the  properties  of  selenium, 
especially  by  Messrs.  Shelford  Bid  well,  J.  W.  Giltay,  Lord 
Ross  and  Sale,  Draper  and  Moss,  Hittorf,  Adams  and  Day, 
Ayrton  and  Perry,  Sir  W.  C.  Siemens , Werner  Siemens,  Mercadier, 
Fritts,Minchin,Ruhmer, Webb, Bell  and  Tainter,and  manyothers. 

Alexander  Graham  Bell  some  twenty  years  ago  made  some 
interesting  experiments  with  his  radiophone ,  a  diagram  of  which 
is  shown  in  Fig.  15,  in  which  a  mica  or  glass  diaphragm  covered 
with  a  silvered  foil  was  used  to  reflect  a  powerful  beam  of  light 
upon  a  selenium  cell  placed  in  the  focus  of  a  silvered  reflector. 


44  HAMMER:  SELENIUM. 

To  the  selenium  cell  were  connected  a  pair  of  telephones  and  a 
battery.  At  the  back  of  the  silvered  diaphragm  was  a  flexible 
tube  and  mouth  piece  into  which  words  were  spoken.  The 
sound  waves  causing  the  diaphragm  to  vibrate  sent  pulsations  of 
the  reflected  light  upon  the  selenium  cell,  producing  correspond-* 
ing  variations  in  its  resistance  and  reproducing  audible  sounds 
in  the  telephone.  Prof.  Bell  only  used  this  over  very  short 
distances. 

In  18  8  Prof.  H.  T.  Simon  of  the  University  of  Gottingen  dis- 
covered that  an  arc  lamp,  the  circuit  of  which  was  in  proximity 
to  a  telephone  circuit,  was  caused  to  vibrate  very  perceptibly 
and  he  devised  his  interesting  speaking  arc  by  means  of  which 
he  superimposed  the  sound  waves  produced  by  the  telephone 
upon  the  circuit  in  which  the  arc  was  placed.  He  connected 
the  lamp  circuit  with  the  secondary  winding  of  an  induction  coil, 


FIG.   15. — Prof.  Bell's  Radiophone. 

the  primary  circuit  being  connected  with  the  carbon  transmitter, 
and  a  battery.  The  sounds  thus  produced  originally  were  very 
weak;  but  by  employing  a  suitable  carbon  microphone,  the 
sound  was  reproduced  to  large  audiences. 

Conversely,  the  arc  could  also  be  used  in  conjunction  with 
telephone  receivers  to  receive  sounds. 

It  is  also  found  that  the  transmitter  battery  may  be  omitted, 
and  a  shunt  taken  from  the  arc  circuit  may  be  used  with  the 
transmitter  and  a  suitable  resistance.  Again,  this  resistance 
may  be  displaced  by  storage  batteries;  and  in  this  case  to 
secure  the  most  satisfactory  results,  self-induction  ("reaction 
coils")  should  be  placed  in  the  circuit  of  the  arc  lamp,  allowing 
the  direct  current  to  pass  without  obstruction ;  but  offering  ex- 
tremely high  resistance  to  the  alternating  currents  produced  by 
the  carbon  transmitter.  By  compensating  in  this  way  any 
disadvantage  in  the  use  of  the  shunt  is  done  awav  with. 


HAMMER:  SELENIUM.  45 

The  transmitter  may  also  be  placed  in  shunt  with  the  reaction 
coil  instead  of  in  shunt  connection  with  the  arc  lamp,  and  this 
has  the  advantage  that  the  rheostat  used  with  the  storage 
batteries  may  be  omitted,  provided  the  windings  of  the  reaction 
coil  are  suitable  for  use  as  a  resistance.  By  this  arrangement, 
the  lack  of  self-induction  in  the  transmitter  circuit  permits  of  a 
very  clear  and  distinct  reproduction,  sufficient  to  be  heard  by 
large  audiences. 

Mr.  W.  Duddell,  of  England,  has  made  some  most  successful 
talking  arcs,  which  the  writer  had  the  privilege  of  seeing  in  Lon- 
don over  two  years  ago.  In  his  arrangement  in  the  secondary 
circuit  is  placed  a  condenser,  which  prevents  the  lamp  current 
entering  the  induction  coil ;  but  allows  the  induction  current  in 
the  transmitter  circuit  to  pass  without  obstruction;  and  this 
arrangement  has  the  effect  of  greatly  increasing  the  sound.  By 
employing  a  condenser  of  from  three  to  five  microfarads,  he 
compensates  for  the  difference  of  phase  produced  by  the  self- 
induction  in  the  circuit,  thus  producing  the  highest  effect  in  the 
arc. 

When  Duddell  uses  the  arc  for  transmitting  sound  waves,  he 
employs  in  the  shunt  circuit  to  the  arc  a  condenser  and  receiving 
telephone.  It  is  advisable  to  employ  as  long  an  arc  as  possible. 
It  has  also  been  found  that  the  Moore  vacuum  tube  and  the 
various  types  of  mercury  arc,  such  as  Arons,  Hewitt  and 
Weintraub,  are  very  suitable  for  this  class  of  work,  as  well  as 
the  carbon  arc;  and  where  the  latter  is  employed,  either  cored  or 
treated  carbons  are  advisable. 

The  theory  advanced  to  account  for  the  phenomena  of  the 
speaking  arc,  is  that  variations  in  temperature  of  the  arc  are  pro- 
duced by  the  variations  of  the  current,  and  the  change  in  the 
Joule  effect  produces  a  corresponding  variation  in  the  volume  of 
the  conductive  gases  in  the  arc. 

The  most  successful  and  most  extensive  experiments  which 
have  been  made  with  the  speaking  arc  are  those  of  Mr.  Ernest 
Ruhmer,  of  Berlin,  Germany,  who  has  employed  it  in  conjunction 
with  his  selenium  cells  for  wireless  telephony  and  with  remark- 
able success.  In  Fig.  16  is  shown  the  apparatus  employed  by  Mr. 
Ruhmer,  with  which  he  has  succeeded  in  transmitting  speech 
over  a  beam  of  light  4£  miles  in  length.*  Mr.  Ruhmer's  ap- 
paratus is  shown  in  the  illustrations  thrown  upon  the  screen, 

*  Mr.  Ruhmer  has  recently  written  the  author  that  he  has  succeeded 
in  talking  over  a  beam  of  light  a  distance  of  over  ten  miles. 


HAMMER:  SELENIUM. 


and  in  Fig.  17.  In  his  experiments  he  employed  an  arc  lamp  with 
a  flaring  arc  6  to  10  mm.  long,  using  an  e.m.f.  of  220  volts.  The 
current  varied  from  4  to  5  amperes  at  1  to  2  k.m.,  8  to  10  amperes 
for  3  to  4  k.m.,  and  12  to  16  amperes  for  5  to  7  k.m.,  and  the 
resistance  of  his  selenium  cell  was  120,000  ohms  in  the  dark,  this 
falling  to  600  ohms  in  full  sunlight.  For  the  transmitting  end, 
Mr.  Ruhmer  employs  a  carbon  transmitter  and  a  battery  super- 
imposing waves  on  the  arc  light  circuit ;  and  the  beam  of  light  is 
reflected  to  some  distant  point,  where  it  is  received  by  a  para- 
bolic reflector,  in  the  focus  of  which  is  placed  a  selenium  cell  con- 
nected with  a  battery  and  a  pair  of  very  sensitive  telephone 
receivers. 


FIG.    16. — Ruhmer's   Apparatus   fur    Long   Distance   Telephony 
over  a  Beam  of  Light. 

Mr.  Ruhmer  has  conducted  extensive  experiments  both  by 
night  and  by  day,  and  even  during  fog  and  rain  on  the  Wannsee, 
near  Berlin.  On  the  screen  you  will  see  an  illustration  of  his 
apparatus  in  actual  work  at  night.  (Fig.  17.) 
^  Some  time  ago  I  suggested  to  Mr.  Ruhmer  the  employment  of 
Edison's  tasimeter,  the  extraordinary  sensitiveness  of  "which  is 
well  known.  He  informed  me  that  he  had  tried  this;  but  had 
found  it  too  "lazy  " ;  and  stated  that  he  has  secured  most  prom- 
ising results  by  the  employment  of  the  thermopile ;  and  with  this 
he  expects  to  be  able  to  transmit  sound  over  many  miles. 


HAMMER:  SELEXIUM.  47 

Mr.  Ruhmer  is  about  to  commence  extensive  experiments 
under  the  direction  of  the  German  Government  in  connection 
with  the  Imperial  fleet  in  the  Baltic  Sea. 

Mr.  Ruhmer  has  also  suggested  the  employment  of  his  photo- 
graphophone,  which  I  shall  describe  later,  as  a  means  of  record- 
ing messages  received  at  a  distance. 

Doubtless  many  present  remember  the  interesting  experiments 
made  by  Mr.  Hayes  at  the  Electrical  Exhibition  held  in  Madison 
Square  Garden  in  May,  1899,  in  which  music  was  transmitted 
over  a  beam  of  light.  At  one  end  of  the  Garden  was  placed  a 
telephone,  before  which  a  cornet  was  played,  causing  waves  of 


FIG.   17.— Ruhmer's  Wireless   Telephone   Receiving   Station   at 
Wannsee,  Berlin  (taken  at  night). 

current  in  the  telephone  circuit  to  be  superimposed  upon  those  in 
a  neighboring  arc  light  circuit.  The  light  rays  from  this  arc 
lamp  were  reflected  across  the  Garden,  where  they  were  received 
in  a  parabolic  reflector  in  the  focus  of  which  was  a  glass  bulb  con- 
taining filaments  of  carbon.  This  bulb  was  connected  to  a  pair 
of  ordinary  phonograph  listening  tubes.  The  varying  light 
which  fell  upon  the  carbon  caused  variations  of  temperature 
inside  of  the  glass  bulb  which  produced  the  original  sounds  in  the 
listener's  ear.  A  bulb  simply  coated  with  lamp  black  and  con- 
taining nothing  but  air,  would  answer  the  purpose  just  as  well. 

Selenium  cells  may  vary  in  resistance  from  2,000  ohms  to 
500,000  ohms  or  more  in  the  dark;   and  certain  cells  may  be  five 


48  HAMMER:  SELENIUM. 

to  twenty  times  as  good  conductors  of  electricity  in  light  as  in  the 
dark;  and  in  the  case  of  other  cells,  notably  that  of  the  Fritts 
cell,  which  I  have  here  this  evening,  and  that  of  the  Ruhmer  cell 
used  in  his  Wannsee  experiments,  will  have  two  hundred  times 
the  conductivity  in  light  that  it  has  in  the  darkness;  and  the 
ratio  may  be  even  higher.  They  are  usually  made  by  winding 
carefully  two  separate  lengths  of  wire,  either  of  copper,  brass, 
German  silver  or  platinum,  equidistant  throughout  their  entire 
length  upon  such  substances  as  slate,  glass,  mica  or  porcelain. 
The  selenium  is  then  spread  thinly  over  the  wires,  forming  an 
insulation  between  the  two  windings.  This  form  of  cell  was 
invented  by  Mr.  Shelford  Bidwell,  F.  R.  S.  No  small  amount  of 
skill  is  necessary  to  wind  these  fine  wires  evenly  and  equidistant, 
and  to  cover  successfully  these  wires  with  the  selenium  coating. 
One  way  of  coating  frequently  employed  is  to  warm  the  cell  on 
a  metal  plate  or  sand  bath  heated  by  a  Bunsen  burner.  When  the 
stick  of  selenium  laid  on  the  plate  shows  evidence  of  melting, 
which  takes  place  at  about  120°  Centigrade,  it  is  drawn  slowly 
over  the  wires,  coating  the  same  thinly  and  evenly.  A  steel 
spatula  or  a  strip  of  mica  can  be  used  with  advantage. 

Or  the  strip  of  material  on  which  the  wires  have  been  wound 
would  be  laid  upon  a  brass  plate  covered  by  a  strip  of  this  mica, 
this  being  placed  upon  a  tripod  with  a  Bunsen  burner  underneath. 
Powdered  vitreous  selenium  may  thus  be  spread  evenly  over  the 
wires,  and  the  selenium  will  shortly  melt,  and  where  the  portions 
of  it  crystallize,  forming  hard  lumps,  it  will  be  necessary  to  con- 
tinue the  heating  until  these  disappear.  Then  the  selenium  may 
be  spread  uniformly  with  a  piece  of  steel,  or  better  still,  a  strip  of 
mica,  care  being  taken  to  cover  up  the  edges.  Mr.  Bidwell  states 
that  the  temperature  should  be  carefully  regulated,  as  when  it  is 
too  low  hard  crystalline  lumps  will  form,  and  when  too  high  the 
surface  tension  causes  the  selenium  to  form  in  drops,  and  it  is 
then  as  difficult  to  spread  as  if  it  were  mercury.  The  proper 
temperature  should  be  only  just  above  217°  Centigrade;  and 
then  the  selenium  is  in  a  plastic  semi-fluid  condition  and  can  be 
easily  manipulated.  When  a  satisfactory  surface  is  secured,  the 
cell  should  be  placed  upon  a  thick  copper  plate  to  cool  quickly, 
when  the  selenium  becomes  black  and  lustrous.  The  Bunsen 
flame  should  then  be  turned  down  to  give  a  temperature  of  about 
120°,  and  the  cell  is  then  placed  upon  the  hot  plate ;  and  shortly, 
the  whole  surface  of  these  turns  to  a  dull  gray  color.  The  tem- 
perature is  then  cautiously  raised  until  signs  of  melting  begin  to 


HAMMER:  SELENIUM. 


1!) 


appear,  generally  near  one  of  the  edges.  When  this  occurs,  the 
burner  is  instantly  withdrawn  and  the  flame  lowered.  The  dark 
spot  recrystallizes  in  the  course  of  a  few  seconds,  and  the  burner 
is  then  replaced  and  left  for  four  or  five  hours,  during  which  time 
the  Se  should  be  only  a  few  degrees  below  the  melting  point. 
The  coil  should  then  be  gradually  cooled  by  lowering  the  flame 
gradually  for  an  hour.  This  process  of  long  heating  and  slow 
cooling  is  generally  spoken  of  as  "annealing. " 

In  Fig.  18  is  shown  an  illustration  of  a  number  of  types  of 
selenium  cells,  including  the  Bidwell,  Ruhmer,  Giltay,  Webb, 


FIG.   18.— Types  of  Selenium  Cells. 


Clausen  and  Bronck,  Mercadier  and  Fritts,  which  I  have  brought 
with  me  for  your  consideration. 

The  two  cells  to  the  extreme  right  and  left  are  modifications  of 
Mr.  Shelford  Bidwell 's  cells,  the  original  form  of  which  consisted 
of  two  fine  copper  wires  wound  side  by  side  on  oblong  strips  of 
mica  with  melted  selenium  spread  over  the  surface,  the  one  to  the 
left  being  manufactured  by  Ernest  Ruhmer,  of  Berlin,  and  by 
Messrs.  Clausen  and  Bronck,  which  consists  of  copper  wire  wound 
on  slate.  The  one  to  the  right  is  manufactured  by  Mr.  J.  W. 
Giltay,  of  Delft,  Holland,  and  consists  of  platinum  wire  wound 
on  slate  and  covered  with  selenium.  The  four  tiny  cells  shown 
against  the  white  background  are  made  by  Mr.  Hartwell  W. 


50 


HA  MMER :  SELEN1 UA1 . 


Webb,  of  New  York  City,  and  consist  of  German  silver  wire 
wound  on  slate.  The  cell  to  the  right  is  placed  in  a  sealed  flat 
glass  tube.  The  two  lower  Webb  cells  are  incased  in  ebonite. 
The  small  round  cell  is  a  tiny  Mercadier  cell  made  by  Mr.  Webb. 
The  method  of  making  the  Mercadier  cell  is  to  use  two  narrow 
ribbons  of  sheet  brass  or  foil,  separated  by  a  ribbon  of  parchment 
paper  rolled  up  like  a  spiral  spring.  This  is  held  between  wooden 
clamps,  one  surface  being  ground  and  polished  off  smoothly,  and 
a  thin  layer  of  selenium  being  spread  over  it.  An  excellent  idea 
of  this  cell  may  be  had  by  noting  Fig.  19,  which  shows  the 
standard  form. 

In  the  center  of  the  picture  is  shown  a  cell  of  Mr.  C.  E.  Fritts, 
of  New  York  City,  for  which  I  am  indebted  to  my  friend 
Prof.  Geo.  F.  Barker.  In  the  Fritts  cell  a  very  thin  layer  of  selen- 
ium from  one  one-thousandth  to  one  five-thousandth  of  an  inch 


FIG.   19. — Mercadier's  cell  (block  and  dotted  lines  represent  the 
two  ribbons  of  brass) . 

in  thickness  is  spread  upon  a  plate  of  metal,  generally  zinc  or 
brass.  The  selenium  and  metal  plate  form  a  chemical  combina- 
tion sufficient  at  least  to  cause  the  selenium  to  adhere  and  make 
good  electrical  connection.  The  upper  surface  of  the  selenium 
is  then  covered  by  a  transparent  conductor  of  electricity,  prefer- 
ably a  thin  film  of  gold  leaf.  Platinum  or  silver  may  also  be 
employed.  Thus  the  two  surfaces  of  the  selenium  are  covered 
by  a  metal  and  are  connected  to  the  two  ends  of  the  circuit. 
The  upper  or  gold  leaf  surface,  however,  permits  the  light  to 
pass  through  and  affect  the  resistance  of  the  selenium  beneath. 
The  tall  cell  in  the  lamp  socket  shown  is  the  latest  form  of  Mr. 
Ruhmer's  cell,  and  this  type  represents,  I  believe,  the  most  im- 
portant development  which  has  been  made  in  the  selenium  cell, 
and  it  has  now  become  most  stable  and  responds  most  rapidly 
to  variations  in  illumination.  He  employs  two  copper  wires, 


HAMMER:  SELENIUM.  51 

wound  spirally  side  by  side  around  a  cylinder  of  porcelain, 
which,  after  the  wires  have  been  covered  with  selenium,  is 
placed  inside  of  a  globe,  from  which  the  air  is  exhausted,  and 
it  is  mounted  with  a  butt  similar  to  an  Edison  incandescent 
lamp,  and  resembles  a  candelabra  lamp.  This  makes  a  most 
convenient  method  of  handling  the  cell;  and  by  keeping  it 
from  the  air  the  disadvantages  inherent  in  all  cells  heretofore 
have  been  very  largely  done  away  with. 

Another  form  of  Ruhmer  cell  consists  of  two  fine  platinum 
wires  wound  on  a  glass  cylinder  1£  inches  long  and  f  of  an  inch 
in  diameter;  the  wires  which  are  1/32  of  an  inch  apart  are  coated 
with  selenium. 

Selenium  cells  are  very  susceptible  to  moisture,  and  it  is  largely 
this  taking  up  of  moisture  which  produces  the  electrolytic  effect 
in  the  cell,  enabling  one  to  connect  it  with  a  galvanometer  and 
produce  a  current  by  merely  focusing  the  light  upon  the  cell. 
This  phenomenon  gave  rise  to  the  designation  of  the  photo- 
electric cell. 

Those  who  have  worked  with  selenium  cells  know  that  hereto- 
fore they  have  been  most  unreliable;  varying  their  resistances 
from  time  to  time  enormously;  and  in  the  case  where  copper 
wires  are  employed,  there  is  a  selenide  of  copper  formed,  which 
often  renders  the  cells  inoperative  in  a  comparatively  short  time. 

To  some  extent,  the  cells  made  originally  have  been  protected 
by  covering  them  with  mica  or  lacquer  or  varnish;  but  placing 
them  in  an  exhausted  receptacle  and  mounting  them  in  the 
manner  devised  by  Mr.  Ruhmer  is,  it  seems  to  the  writer,  a  most 
important  step  in  the  commercial  development  of  the  selenium 
cell. 

Prof.  Bell  has  made  a  number  of  types  of  selenium  cells,  his 
standard  form  consisting  of  alternate  disks  of  brass  and  mica, 
with  the  mica  disks  slightly  smaller  than  the  brass,  forming  a 
recess  for  holding  the  selenium,  which  is  spread  over  the  surface. 
All  the  evenly  matched  disks  are  connected  to  one  end  of  the 
circuit,  and  all  the  old  disks  to  the  other  end.  The  cylindrical 
form  of  the  cell  enables  it  to  be  acted  upon  from  all  directions, 
when  placed  lengthwise  in  the  focus  of  a  parabolic  reflector. 
This  is  also  of  great  advantage  in  the  Ruhmer  type  of  cell. 

Selenium  cells  possess  the  remarkable  property  of  recovering 
the  original  resistances  upon  the  removal  of  the  source  of  light. 

It  is  well  known  that  in  the  case  of  the  radiophone,  if  a  beam  of 
sunlight  be  thus  intercepted  by  a  blackened  perforated  revolving 


52  HAMMER:  SELENIUM. 

disk,  a  musical  note,  varying  in  pitch  with  the  speed  of  the  disk, 
will  be  produced  in  a  rubber  tube  held  at  the  opposite  side  of  the 
disk.  I  have  here  one  of  the  original  forms  of  radiophones. 

A  piece  of  apparatus  has  been  devised  consisting  of  a  disk  with 
slits  near  the  edge,  which  is  placed  near  an  incandescent  lamp, 
and  a  selenium  cell.  If  the  selenium  cell  is  connected  to  a  tele- 
phone and  battery,  and  the  disk  is  rapidly  revolved,  a  musical 
note  will  be  produced  in  the  telephone,  the  pitch  of  which  will 
correspond  to  the  speed  of  the  revolving  disk. 

Mr.  Giltay  has  recently  written  me  suggesting  a  very  pretty 
experiment  in  this  line,  in  which  a  double  vaned  Crookes'  radio- 
meter is  placed  between  a  selenium  cell  and  an  arc  light  shielded  by 
an  alum  cell.  The  light  from  the  arc  lamp  causes  the  radiometer 
to  revolve  intermittently,  screening  the  selenium  cell  and  produc- 
ing a  musical  note  in  the  telephone  attached  thereto,  the  pitch 
of  which  is  in  accordance  with  the  speed  of  revolution  of  the 
radiometer. 

I  have  here  to-night  two  forms  of  flame  telephone  trans- 
mitters, one  of  which  was  presented  to  me  by  Mr.  Ruhmer, 
and  the  other  I  have  purchased  from  Mr.  Giltay,  which  I 
have  mounted  as  you  see  it  here  and  as  illustrated  in  Fig.  20 
(about  24  volts  are  required,  depending  upon  the  selenium 
cell).  In  each  case  you  will  note  that  I  have  an  acetylene 
generator  which  conveys  gas  to  the  interior  of  an  otherwise 
empty  telephone  transmitter.  The  diaphragm  of  these  trans- 
mitters is  made  of  pig-skin,  or  a  similar  material.  A  tiny  pipe 
runs  from  the  back  of  the  transmitter,  and  ends  in  one  case 
to  a  single  acetylene  jet,  and  in  the  other  case  to  three  acety- 
lene jets.  By  talking  against  the  pig-skin  diaphragm,  the  gas 
inside  is  made  to  vibrate  and  produces  a  manometric  flame. 
This  flame  throws  its  light  upon  a  selenium  cell,  to  which  is  con- 
nected a  battery  and  a  pair  of  very  sensitive  telephones  between 
100  and  200  ohms  for  each  cell  of  battery,  in  which  the  sounds 
spoken  into  the  transmitter  are  most  perfectly  reproduced.  A 
thin  sheet  of  paper  inserted  between  the  flame  and  the  selenium 
cell  serves  to  cut  off  all  sound.  It  is  self-evident  that  these 
telephone  receivers  might  be  at  any  distant  point.  I  have  worked 
them  over  considerable  distances. 

In  Fig.  21  are  shown  a  number  of  most  interesting  applications 
of  the  selenium  cell  in  conjunction  with  a  battery  and  relay,  used 
for  starting  a  motor,  ringing  a  bell,  firing  a  cannon,  blowing  a 
horn,  and  lighting  incandescent  lamps,  all  of  which  experiments 


HA  MMER :  SELENI UM . 


63 


I  shall  hope  to  show  you  in  actual  operation,  as  I  have  had  them 
working  most  successfully  in  my  laboratory;  and  you  will  see 
that  by  merely  passing  my  hand  before  the  selenium  cell,  I  can 
start  and  stop  the  motor,  turn  the  light  on  and  off,  and  ring  the 
bell  and  blow  the  horn,  or  I  can  fire  this  cannon,  start  my  phono- 
graph talking,  etc.  I  am  indebted  to  the  courtesy  of  the  Marconi 
Co.  for  the  large  relay  used  in  certain  of  these  experiments. 

I  have  here  also  a  3  h.p.  motor,  driving  a  H  k.w.  generator  and 


FIG.    20.— Manometric     Acetylene      Flame     Transmitter    with 
Selenium  Cell,  etc.— (a  battery  of  about  24  volts  employed). 

supplying  these  lamps  which  have  been  courteously  supplied  by 
the  General   Electric   Co.;   and  by  means  of  this  selenium  cell, 
relay   battery  and  a  motor  starter,'  for  which  I  am  indebted  t 
the   Cutler-Hammer   Co.,    I  hope  to  be  enabled  to  start  and 
stop  the  motor  by  merely  passing'my  hand  before  the  selem 

cell. 

In   Fig.   22  is  shown  a  portiorTof  the  stage  setting  at 


54 


PI  A  AIMER:  SELENIUM 


HAMMER:  SELENIUM.  55 

lecture,  and  shows  in  the  foreground  the  three  horse-power 
motor  and  generator  which  supplied  a  bank  of  lamps,  and 
which  plant  was  started  and  stopped  many  times  when  the  au- 
thor passed  his  hand  between  the  acetylene  flame  and  a  selenium 
cell.  The  frontispiece  is  a  general  view  of  the  stage  setting  in 
the  College  of  the  City  of  New  York,  and  was  taken  shortly  be- 
fore Mr.  Hammer's  lecture. 

^  In  1886  the  writer  attended  a  convention  of  the  Edison  Asso- 
ciation of  Illuminating  Companies  at  Rochester,  New  York,  and 


FIG.  22. — Three  H.P.  Motor  and  Generator  supplying  Bank  of  Lamps 
and  operated  by  shielding  with  the  hand  a  Selenium  cell  from 
an  Acetylene  Flame. 

during  a  discussion  of  contract  systems  versus  meter  systems,  he 
gave  his  experience  as  chief  inspector  of  central  stations  of  the 
Edison  Company,  in  dealing  with  the  difficulties  met  with  in 
supplying  light  by  contract;  and  he  then  described  a  prac- 
ticable method  of  utilizing  selenium  cells  to  control  relays  and 
magnets  which  would  throw  off  the  electric  lights  on  the  approach 
of  day  and  on  again  at  night,  thus  solving  the  difficulty  of  street 
lighting,  and  other  circuits  intended  to  operate  only  at  night. 
On  February  12,  1890,  in  a  paper  on  some  experiments  with 


56  HAMMER:  SELENIUM. 

selenium  cells,  Mr.  Shelf ord  Bidwell  showed  a  relay  operated  by  a 
selenium  cell,  which  threw  on  an  electric  lamp  and  rang  a  bell; 
and  he  suggested  the  protection  of  safes  and  strong  rooms  by 
selenium  cells,  which  would  be  affected  by  the  light  from  a 
burglar's  lantern,  thus  giving  an  alarm.  He  also  spoke  of  their 
being  used  to  give  notice  of  the  extinction  of  railway  signal  lamps 
and  ship  lights,  and  stated  the  following:  "But  I  do  not  at 
present  attach  any  serious  importance  to  such  practical  applica- 
tions of  these  devices.  I  regard  them  simply  as  offering  some- 
what attractive  illustrations  of  the  effect  of  light  upon  the  resist- 
ance of  selenium. " 

This  is  an  important  statement  from  the  greatest  authority  on 
the  subject  of  selenium,  but  to-day  it  will  not  hold  good. 

I  hold  in  my  hand  a  small  vial  containing  some  "thermit," 
which  was  discovered  by  Dr.  Goldschmidt.  It  consists  of  oxide 
of  iron,  such  as  one  would  get  off  of  a  blacksmith's  anvil,  or  from 
the  rolls  of  a  rolling  mill,  and  is  mixed  with  powdered  metallic 
aluminum.  A  red  hot  iron  or  molten  cast  iron  poured  into  this 
mixture  produces  no  effect ;  but  if  a  little  barium  preparation  or 
magnesium  powder  be  placed  on  top  of  this  mixture  and  touched 
off  by  a  match,  an  extraordinary  reaction  takes  place,  producing 
a  temperature  of  about  3000°  C.,  and  the  mechanical  equiva- 
lent of  a  kilo  (2.2  Ibs.)  of  thermit  is  about  1,730  horsepower  sec- 
onds or  1,273  kilowatt  seconds. 

I  have  seen  some  very  interesting  experiments  made  in  welding 
girder  rails,  pipes,  etc.,  by  this  process,  and  have  here  some  inter- 
esting samples  of  manganese,  chromium,  ferro-titanium  and  other 
metals  prepared  in  this  way. 

I  have  also  seen  steel  safes  in  which  enormous  holes  had 
been  burned  by  employing  thermit;  and  it  would  be  possible 
for  a  burglar  to  carry  some  thermit  in  his  pocket  and  burn  a  hole 
in  a  safe  large  enough  to  insert  his  arm  and  extract  the  valuables. 
I  also  saw  in  Germany  last  summer  a  substance  called  "anti- 
thermit,"  which  it  is  intended  to  place  in  the  lining  of  safes  to 
prevent  the  reaction  taking  place,  thus  protecting  the  safe.  But 
a  simple  plan  would  be  to  place  a  selenium  cell  in  or  near  the 
safe,  so  that  the  moment  the  reaction  was  started,  a  signal  would 
be  given  to  the  police  in  a  similar  manner,  as  suggested  by  Mr. 
Bidwell  in  the  case  of  the  burglar's  bull's-eye  lantern. 

An  important  commercial  application  of  the  selenium  cell  has 
recently  been  made  by  Mr.  Ernest  Ruhmer  in  connection  with  his 
.  electrically  controlled  buoy  illustrated  in  Fig.  23. 


HAMMER-    SELENIUM.  57 

Pintsch  has  constructed  a  large  number  of  buoys  containing 
compressed  gas,  which  would  last  from  one  month  to  upwards  of 
a  year;  but  it  was  heretofore  necessary  to  burn  these  lights  day 
and  night,  it  being  often  impracticable  by  reason  of  distance  at 
which  they  were  placed,  and  frequency  of  storms,  etc  to 
switch  off  the  gas  so  that  it  would  not  burn  during  the  daytime. 

Mr.  Ruhmer  has  placed  one  of  his  selenium  cells  in  the 
top  of  such  a  buoy  connected  with  a  switching  device 
which,  as  soon  as  the  sun  rises  in  the  morning,  causes  the 
selenium  cell  to  reduce  its  resistance,  this  causing  the  switching 
device  to  turn  off  the  gas,  which  is  again  turned  on  upon  the 


FIG.  23.— Pintsch  Gas  Buoy  Controlled 
by  a  Ruhmer  Selenium  Cell,  Battery 
and  Switch  Mechanism. 


FIG. 

of 


24. — Diagram  of  Circuits 
'Selenium"  Buoy. 


increase  of  resistance  of  the  selenium  cell  by  the  approach  of 
nightfall,  or  if  desired  in  the  case  of  a  storm  coming  up.  A  buoy 
containing  sufficient  gas  for  one  month  could  thus  be  made  to 
answer  without  recharge  for  from  three  to  five  months. 

The  arrangement  of  the  circuits  as  originally  devised  by  Mr. 
Ruhmer  is  shown  in  Fig.  24.  The  voltmeter  needle  has  been 
replaced  by  a  relay,  and  the  apparatus  simplified.  A  single  dry 
cell  is  interpolated  in  the  selenium  cell  circuit,  as  usually  em- 
ployed on  the  buoy;  and  this  cell  will  last  a  year  or  more,  and 
with  the  relay,  it  is  placed  in  the  bottom  of  the  buoy  and  ar- 
ranged to  be  absolutely  waterproof. 


58  HAMMER:  SELENIUM. 

When  I  was  in  Berlin  last  August,  one  of  these  buoys  had  been 
in  operation  since  the  previous  October,  turning  the  light  on  and 
off  every  night  and  morning;  and  Mr.  Ruhmer  has  recently 
written  me  that  it  is  still  operating  successfully,  as  are  others 
which  he  has  placed  near  Hamburg  and  in  the  Baltic  Sea. 

Mr.  Ruhmer  has  also  constructed  an  apparatus  employing  the 
selenium  cell  to  which  he  has  given  the  name  "  photograph*?  - 
phone,"  which  is  one  of  the  most  remarkable  pieces  of  scientific 
apparatus  that  it  has  ever  been  my  pleasure  to  see.  Figs.  25,  26 


FIG.  25. — Ernest  Ruhmer's  Photographophone,  Showing  Ex- 
terior View,  together  with  Telephone  Transmitter  and  Arc 
Lamp. 

and  27  illustrate  the  general  construction  of  the  apparatus, 
which  I  shall  further  illustrate  by  accompanying  lantern 
slides.  In  Fig.  28  the  apparatus  is  shown  diagrammatically  and 
in  Fig.  27  the  inventor  is  shown  listening  to  the  photograph- 
ophone  reproducing  speech  and  music.  It  consists  of  a 
box  containing  a  gelatine  or  celluloid  film,  such  as  employed 
in  moving  picture  machines,  which  is  driven  at  high  speed 
by  means  of  an  electric  motor.  In  the  front  face  of  the  box  is  set 
a  cylindrical  lens  about  the  size  of  one's  little  finger.  A  short 


HAMMER:  SELENIUM.  59 

distance  away  from  the  box  is  placed  an  arc  lamp  and  a  telephone. 
Words  spoken  or  sung  into  the  telephone  superimpose  the  waves 
in  the  telephone  circuit  upon  the  current  flowing  in  the  arc  light 
circuit,  and  cause  a  corresponding  variation  in  the  light  of  the 
arc.  The  rays  from  the  arc  lamp  pass  through  the  cylindrical 
lens  already  referred  to,  and  are  caused  to  fall  in  sharp  white 
lines  on  the  moving  sensitive  film.  This  film,  upon  being  taken 
out  of  the  box  and  developed,  shows  a  series  of  perpendicular  stri- 
ations  parallel  to  one  another,  which  are  really  a  photographic  rec- 
ord of  the  sound  waves  originally  entering  the  telephone  transmit- 
ter. Where  the  striations  are  fine  and  close  together  the  pitch  is 
high,  but  where  they  are  broader  and  farther  apart  the  pitch  is 
low.  Strips  of  the  films  or  photograms  are  shown  in  Fig.  29.  The 
developed  film  is  next  placed  back  into  the  box  and  the  motor 
again  started.  The  arc  lamp  remains  in  its  original  position,  but 


FIG.  23. — Showing  Interior  of  Ruhmer's  Photographophone. 
burns  steadily  as  the  telephone  is  not  operated.  The  rays  from  the 
arc  lamp  passing  through  the  lens  are  therefore  quite  uniform,  and 
the  moving  gelatine  strip  acts  as  a  screen  to  cut  off  these  rays, 
allowing  the  light  intermittently  to  fall  upon  the  selenium  cell  at 
the  back  of  the  box,  producing  a  variation  in  its  resistance  and  a 
corresponding  effect  in  the  telephone  receivers  connected  thereto. 
A  battery  is  also  interpolated  in  the  circuit  with  the  selenium 
cells  and  the  telephones.  By  holding  these  telephones  to  the  ear, 
the  reproduction  of  the  sound  is  perfect,  as  I  can  vouch  for  from 
personal  experience  with  the  apparatus. 

Mr.  Ruhmer  contemplates  utilizing  this  photographophone  as 
a  receiving  instrument  with  its  wireless  telephone  system,  in 
which  he  employs  a  beam  of  light,  as  already  described. 


60 


HAMMER:  SELENIUM. 


Mr.  Shelford  Bidwell  has  also  made  a  device  for  producing 
pictures  or  writing  at  a  distance  by  combining  the  properties  of 
selenium  with  the  chemical  telegraph. 

Various  inventors  have  endeavored  to  solve  the  problem  of 
seeing  what  goes  on  at  a  distance  by  employing  selenium: 
Among  these  are  Perosino,  Senlecq,  de  Paioa,  Cary,  Sawyer  ,lLar- 
roque,Nipkow,Gemmill,Liesegang,Heinzerling,Edison, Stern  Jan 
Szczepanik,  Dussaud,  Otto  von  Bronk,  von  St.  Schneider,  Ayrton 
and  Perry,  Korn,  and  others,  who  have  proposed  various  methods 
employing  images  thrown  on  ground  glass  or  through  a  photo- 
graph negative,  or  upon  mirrors  swinging  synchronously,  or  by 


FIG.  27. — Mr.    Ernest    Ruhmer   Listening   to   his    Photographo- 

phone. 

using  revolving  perforated  screens,  for  cutting  off  the  beams  of 
light,  multiple  selenium  cells  which  would  be  affected  by  high 
lights  and  low  lights  of  the  original  picture,  etc.,  these  devices 
effecting  some  method  of  illumination  at  the  receiving  end  or 
producing  an  electrochemical  action  such  as  is  produced  by  the 
usual  chemical  telegraph  systems,  or  controlling  .an  electro- 
pantograph  system  such  as  Gray's  telautograph.  These  various 
inventions  have  been  termed  the  telescope,  telephote,  telectro- 
scope  and  the  telephotograph.  But  these  devices  have  thus  far 
reached  little  further  than  descriptive  matter,  drawings  and 
crude  experiments. 

Various  people  have  suggested  the  use  of  selenium  cells  for 
photometric  purposes;    and  it  is  interesting  to  note  that  Mr. 


HAMMER:  SELENIUM. 


til 


Latimer  Clark  suggested  this  application  the  evening  in  which  Mr 
Willoughby-Smith  first  brought  to  public  notice  the  phenomena 
of  variation  in  resistance  of  selenium  when  exposed  to  light,  to 
which  I  have  already  referred. 

Mr.  Fritts  has  suggested  making  a  form  of  photometer  which 
would  be  sensitive  to  lights  of  different  color,  as  well  as  of  varying 
candle  power,  by  employing  as  a  film  on  the  surface  of  his  cell  a 
gold  foil  which  transmits  green  rays,  a  silver  foil  the  blue  rays, 
and  so  on ;  and  suggests  that  a  solid  transparent  conducting  film 
which  would  transmit  all  of  the  rays  would  be  far  better  and  thus 
remove  the  color  stumbling  block  in  photometric  work. 

Sir  William  Crookes  has  constructed  an  exceedingly  interesting 
type  of  radiometer,  in  which  he  has  coated  the  revolving  vanes  on 
one  side  with  selenium,  and  on  the  other  with  chromic  acid.  He 


FIG.   28. — Showing  General  Arrangement  of  Circuits  of  Ruhmer's 
Photographophone. 

found  that  the  white  light  from  a  sperm  candle  repelled  the 
selenium,  while  the  yellower  light  of  the  wax  candle  repelled  the 
chrome,  thus  indicating  the  relative  absorptive  powers  of  the 
different  substances  for  rays  of  different  refrangibility,  resulting 
in  mechanical  motion;  just  as  the  same  selective  capacity 
operates  in  photography  as  chemical  action. 

In  1891  Prof.  Barnard  of  Lick  Observatory  employed  a 
selenium  cell  as  a  device  for  automatically  detecting  comets,  and 
Minchin  has  employed  the  selenium  cell  quite  extensively  in  his 
astronomical  investigations. 

In  Fig.  30  is  shown  a  curve  which  Mr.  Ruhmer  recently  sent  me 
which  shows  some  observations  made  by  means  of  his  selenium 
cell  during  an  eclipse,  these  being  the  only  observations  which 
anyone  was  enabled  to  make  at  that  time,  on  account  of  stormy 
weather.  Mr.  Ruhmer  has  prepared  an  interesting  paper  bearing 
on  this  and  other  applications  of  the  selenium  cell  to  meteorology. 
He  made  his  observations  on  October  31,  1902. 


62  HAMMER:  SELENIUM. 

Selenium  is  found  in  Vesuvian  lava,  and  in  natural  sulphur  as  a 
sulphur  selenide  in  the  Lispari  Islands.  It  is  also  found  in 
Norway  and  other  iron  pyrites.  It  occurs  in  meteoric  iron  and 
in  such  rare  metals  as  eucarite  as  a  selenide  of  silver  and  copper 
in  Sweden  and  Chili;  crooksite,  a  selenide  of  copper  and  thallium 
with  a  little  silver,  from  Norway;  as  clausthalite,  a  selenide  of 
lead  in  the  Hartz  Mountains,  from  Zinken  and  Claustbal,  in 
Inverg,  Rheinberg,  Saxony,  Rio  Tinto,  Spain,  Mcndcza,  South 
America;  as  riolite  at  Culebras,  Mexico;  as  Lehrbachite,  a 


" 


FIG.  29. — Photogram  as  used  in  Ruhmer's  Photographophone 
(High  Pitch  Tones  above,  Low  Pitch  below). 

selenide  of  msrcury  and  lead  from  the  Hartz  Mountains;  as 
zorgite,  a  selenide  of  copper  and  kad  from  Glasbach  in  the  Hartz 
Mountains.  Selenium,  although  widely  distributed  over  the 
globe,  occurs  only  in  small  quantities  and  in  some  instances 
is  found  in  native  state. 

Selenium  is  placed  among  the  rare  metals.  Chemically  pure 
crystalline  selenium  costs  about  $1.00  per  gramme;  and  the 
ordinary  commercial  article  about  10  cents  per  gramme. 

The  Bibliography  of  selenium  is  quite  extensive.  Those  inter- 
ested in  the  subject  will  find  an  excellent  paper  by  Mr.  A.  P. 


HAMMER:  ULTRA-VIOLET  RAYS. 


63 


Saunders  in  the  Jour,  of  Ckem.  for  June,  1900.   The  paper  contains 
many  references,  and  is  entitled  "Allotropic  Forms  of  Selenium." 


FIG.   30.— Curve  Taken  with  Ruhmer  Cell  During  Eclipse    Oct 
31,  1902. 

THE  TREATMENT  OF  DISEASE  BY  ULTRA-VIOLET  RAYS. 

Some    professional  matters 
detained  the  writer  in  Copen- 
hagen last  summer  for  several 
weeks,  and  during  his  stay  in 
that  city  he  had  the  privilege 
of  visiting    the  Finsen  Light 
Institute  at   Rosenvaengat,  a 
suburb   of  Copenhagen,    and 
was    enabled    to     investigate 
the  system  for  the  treatment 
of  disease    by   light,   inaugu- 
rated by  Dr.  Niels  R.  Finsen. 
In  Figs.  31  and  32  are  shown 
views  of  the  operating   room 
at  the  Finsen  Institute,  where 
a    large    number   of  patients 

PROF.  NIELS  R.  FINSEN.  from  various  parts  of  Europe 

were  undergoing  treatment  at  the  time  of  my  visit. 
Dr.  Finsen  has  conducted  very  extensive  and  most  painstaking" 


64  HAMMER:  ULTRA-VIOLET  RAYS. 

researches  into  the  bactericidal  effects  of  light,  and  he  has 
found  the  violet  end  of  the  spectrum  to  possess  remarkable 
curative  powers,  and  he  has  also  found  that  by  utilizing 
the  blue,  violet  and  ultra-violet  rays  of  the  spectrum,  those 
loathsome  diseases  of  tuberculosis  of  the  skin  and  lupus,  diseases 
which  have  baffled  surgical  skill  heretofore,  have  been  success- 
fully combated. 

It  has  recently  been  stated  that  in  New  York  City  alone  there 
are  annually  20,000  cases  of  tuberculosis,  with  8,000  deaths;  and 
there  is  probably  no  disease  with  which  mankind  is  afflicted 
which  compares  in  deadly  character  to  tuberculosis. 

In  affecting  certain  of  the  internal  organs,  it  is  known  as  con- 
sumption, and  appearing  externally,  attacking  the  skin  and 
underlying  tissues,  it  is  known  as  lupus  vulgaris.  As  a  rule,  it 
appears  in  single  patches,  most  frequently  attacking  the  face, 
especially  the  nose,  cheek  and  mouth.  It  may,  however,  attack 
the  extremities,  or,  in  fact,  any  portion  of  the  body  and  even 
mucous  membranes.  Fortunately,  lupus  is  rather  rare  in  this 
country,  although  very  common  in  Europe. 

Koch  and  others  have  fully  demonstrated  that  tuberculosis  is 
due  to  the  presence  of  specific  organisms  named  "tubercle 
bacilli,"  which  have  been  found  to  be  present  in  both  the  internal 
and  cutaneous  forms  of  the  disease. 

Doubtless  many  present  remember  the  "blue  glass  craze" 
which  swept  over  the  country  in  1876,  or  thereabouts. 

I  have  with  me  here  a  copy  of  General  A.  J.  Pleasonton's  book 
entitled  "Blue  and  Sunlights,  Their  Influence  upon  Life  and 
Disease,"  which  I  picked  up  in  a  second-hand  book  store  some 
years  ago;  and  I  would  commend  the  examination  of  this  book 
to  all  who  are  interested  in  the  subject.  General  Pleasonton  and 
his  system  were  condemned  to  both  abuse  and  ridicule.  Dr. 
Finsen,  however,  says,  "The  General  was  absolutely  on  the  right 
track." 

For  a  considerable  time  Finsen 's  work  received  little  credence 
and  no  encouragement;  but  he  persisted  in  his  investigations, 
and  the  results  secured  by  him  finally  bore  fruit,  and  to-day  the 
world  rings  with  his  praises.  In  all  parts  of  the  civilized  world 
his  work  is  being  taken  up,  and  institutes  are  being  founded  for 
the  treatment  of  disease  by  light  rays — particularly  the  ultra- 
violet light.  In  England  the  initiative  was  taken  by  Queen 
Alexandra,  and  in  Russia  by  her  sister,  the  Czarina,  they  both 
investigating  the  system  while  visiting  their  father,  the  King  of 


HAMMER     ULTRA-VIOLET  RAYS. 


65 


FIG.   31  — Showing    Main    Operating    Room,    Finsen    Institute, 
Copenhagen. 


FIG.  32. — Showing  Arc  Lamp  and  Four  Finsen  Tubes  in  Use 
at  One  Time. 


66  HAMMER:  ULTRA-VIOLET  RAYS. 

Denmark.    Much  has  also  already  been  done  in  the  United  States. 

It  will  be  remembered  that  during  Queen  Elizabeth's  reign  a 
certain  court  physician  recommended  strongly  that  patients 
suffering  from  smallpox  should  be  kept  in  a  room,  the  decora- 
tions of  which,  including  the  hangings,  bed  draperies,  etc., 
should  be  red  in 'color,  claiming  that  the  red  light  had  a 
soothing  effect  upon  the  irritated  portions  of  the  skin,  lessening 
the  severity  of  the  disease.  Little  importance  was  attached  to 
this  method,  and  the  originator  of  it  was  branded  as  a  Charlatan. 

Prof.  Finsen  has,  however,  found  that  this  method  of  treat- 
ment of  smajipox,  is  of  paramount  importance.  He  has  placed 
patients  in  a  room  into  which  the  sun's  rays  could  only  penetrate 
through  sheets' 'of  red  glass,  just  as  they  would  penetrate  a 
photographic  dark  room ;  and  he  has  found  that  patients  placed 
in  such  a  room  prior  to  the  most  painful  and  most  dangerous 
suppuration  stage  setting  in,  that  suppuration  has  been  entirely 
prevented  and  that  the  scarring  has  been  in  nearly  all  cases  abso- 
lutely prevented,  and  in  the  few  cases  where  there  was  any  scar- 
ring, it  was  hardly  perceptible.  The  disease  has  been  in  a  much 
milder  form,  the  fever  usually  accompanying  the  eruption  dis- 
appearing, and  the  temperature  remaining  normal.* 

He  has  found  that  the  use  of  ultra-violet  light  on  these  pa- 
tients very  much  aggravated  the  disease,  and  even  in  cases  where 
patients  were  almost  cured  and  they  have  been  allowed  to  go  out 
into  the  sunlight,  the  disease  has  at  once  been  aggravated. 

In  connection  with  his  investigations  into  the  effects  of  light 
Finsen  made  some  interesting  and  ingenious  experiments  upon 
earth-worms  placed  in  a  box,  one-half  of  which  was  covered  with 
red  glass  and  the  other  half  blue  glass;  and  he  found  the  blue 
light  irritated  the  worms  so  they  invariably  crawled  under  the 
red  glass,  and  a  chameleon,  placed  with  its  body  midway  between 
the  glasses,  turned  almost  jet  black  under  the  influence  of  the 
blue  rays,  while  that  portion  under  the  red  glass  remained  nearly 
white,  which  Prof.  Finsen  says  showed  that  the  chameleon  was 
altering  its  pigment  cells  to  lessen  the  irritating  effects  of  the 
blue  light. 

The  ultra-violet  end  of  the  spectrum  contains  the  most  re- 
frangible rays,  and  it  is  these  rays  which  are  so  harmful  in  cases 
of  smallpox;  and  t  is  also  these  actinic  rays  which  produce  sun- 

*  Prof.  Finsen  has  recently  written  the  author  that  placing  the  patients 
in  a  dark  room  is  fully  as  efficacious  as  placing  them  in  a  room  lighted 
with  red  rays  only,  the  important  thing  being  to  keep  the  patient  from 
exposure  to  the  actinic  rays. 


HAMMER:  ULTRA-VIOLET  RAYS.  07 

burning,  which  one  often  experiences  in  the  Alps,  or  any  high 
altitude  where  the  temperature  may  be  considerably  below 
zero;  and  there  are  doubtless  many  present  who  have  experi- 
enced considerable  effect  similar  to  sunburning  by  working  in 
close  proximity  to  arc  lamps. 

While  these  ultra-violet  rays  are  so  harmful  in  the  case  of 
smallpox,  they  are  of  the  precise  nature  which  is  most  desirable 
in  the  treatment  of  such  diseases  as  tuberculosis  of  the  skin  or 
lupus  vulgaris.  These  rays  not  only  destroy  the  bacilli,  but  they 
excite  and  stimulate  nutrition  and  excite  activity  in  granulation, 
thus  assisting  very  greatly  in  the  rapid  recovery  from  the  disease. 

Doubtless  the  rays  emanating  from  the  sun  are  very  rich  in 
blue,  violet  and  ultra-violet  light;  but  the  atmosphere  readily 
absorbs  these  rays,  and  while  Prof.  Finsen  for  a  time  used  the 
sun's  rays  in  the  treatment  of  tuberculosis  of  the  skin  and  lupus 
he  found  that  by  employing  the  arc  light  the  same  effect  could 
be  produced  in  a  very  much  shorter  space  of  time ;  and  that  he 
was  in  this  way,  also,  independent  of  weather  conditions. 

The  arc  light  is  much  richer  in  ultra-violet  rays  than  the  sun- 
light ;  and  Broca  and  Chatin  of  Paris  have  found  that  by  placing 
an  iron  core  inside  of  the  positive  carbon  electrode,  this  arc  was 
still  richer  in  ultra-violet  light,  and  Gorl  of  Erlangen  has  con- 
structed a  form  of  aluminum  arc,  in  which  four  arcs  were  formed 
between  five  aluminum  electrodes.  I  have  here  a  modification 
of  Gorl's  lamps  constructed  by  Messrs.  Waite  &  Bartlett  of  this 
city,  in  which  there  are  four  iron  electrodes  forming  three  iron 
arcs  in  series,  which  produce  an  intense  source  of  ultra-violet 
light,  which  I  shall  presently  show  in  operation. 

Bang  and  others  have  also  made  arc  lamps  employing  ter- 
minals of  iron. 

It  is  claimed  that  by  employing  the  iron  arc  the  same  results 
which  take  an  hour  and  ten  minutes  by  means  of  the  carbon  arc 
can  be  accomplished  in  twenty  minutes  to  half  an  hour;  and  also 
that  so  intense  are  these  ultra-violet  rays  it  is  not  necessary  to 
use  pressure  to  drive  the  blood  away  from  the  diseased  part,  and 
it  is  also  unnecessary  to  use  water  to  cool  the  rays.* 

Drs.  Piffard  and  Jamieson  have  suggested  the  use  of  suprarenal 
extract  in  the  form  of  adrenalin  chloride,  which  the  former 
prefers  to  introduce  into  the  skin  around  the  diseased  spot 

*  Prof    Finsen  has  recently  written  the  author  emphatically  asserting 
that  iron  electrodes  are  not  as  efficacious  as  carbon  electrodes  as  the  rays 
from  the  iron  arc,  he  claims,  do  not  penetrate  as  deeply  as  the  rays  f 
the  carbon  arc. 


68  HAMMER:  ULTRA-VIOLET  RAYS. 

by  cataphorisis,  thus  producing  a  whitened  area  from  which 
the  blood  has  been  withdrawn,  which  enables  the  treatment  of 
this  portion  by  the  ultra-violet  light,  without  pressure  being  ap- 
plied, and  the  blood  does  not  return  for  half  an  hour  or  more. 
The  cataphoric  electrode  is  covered  with  a  thickness  of  lentine 
saturated  with  adrenalin  connected  with  a  positive  pole  of  the 
battery,  using  a  current  of  from  three  to  four  milli-amperes,  the 
bleaching  taking  from  four  to  five  minutes'  time. 

The  Roentgen  rays  have  been  found  very  effective  in  the 
treatment  of  certain  diseases,  especially  where  hard  tubes  are 
employed,  and  as  we  are  considering  particularly  the  treatment 
of  lupus  vulgaris,  I  would  call  attention  to  Fig.  33,  which  repre- 


FIG.  33. — Lupus  Vulgaris  Cured  by  X-rays. 

sents  a  patient  treated  by  my  friend  Dr.  William  H.  King  of  this 
city,  in  which  the  X-rays  successfully  cured  a  case  of  lupus 
vulgaris  brought  on  by  the  patient's  pricking  a  tiny  boil  on  the 
side  of  his  nose  with  a  pin  taken  from  the  lapel  of  the  coat  of  a 
friend  who  was  suffering  from  tuberculosis  (consumption).  The 
rapid  progress  of  the  disease  is  shown  in  the  illustration  and  was 
taken  three  weeks  after  using  the  pin,  and  was  largely  aug- 
mented by  the  man's  age  (45),  and  his  being  in  poor  health  (a 
chronic  rheumatic).  Two  bacteriological  examinations  showed 
conclusive  evidence  of  the  presence  of  tubercle  bacilli. 

In  Fig.  34  is  shown  the  original  blue  lens  used  by  Finsen  when 
employing  sunlight.  It  consists  of  a  flask  full  of  light  blue 
ammoniacal  sulphate  of  copper.  The  bottle  with  its  contents 


HAMMER:  ULTRA-VIOLET  RAYS. 


69 


makes  a  plano-convex  lens.  The  sunlight  passing  through  this 
is  found  to  work  very  well ;  but  it  was  too  slow,  and  the  sun  was 
frequently  obscured.  Finsen  later  used  plain  water,  finding  that 
the  blue  water  cut  off  most  of  the  ultra-violet  rays  and  he  found 
the  clear  water  very  largely  absorbed  the  ultra-red  rays  which 
caused  the  heat. 

In  Fig.  35  is  shown  a  form  of  telescope  which  is  now  adapted  in 
standard  practice  at  the  Finsen 
Institute.  It  contains  four  rock 
crystal  lenses,  which  act  to  cut 
off  considerable  of  the  heat  rays ; 
but  allow  the  ultra-violet  light 
to  pass  through  it. 

It  will  be  remembered  that 
ordinary  glass  cuts  off  almost 
all  of  the  ultra-violet  rays, where- 
as a  block  of  rock  crystal  4.4  mm. 
thick  will  allow  60  per  cent,  of  the 
ultra-violet  to  pass  through  it. 

A  part  of  the  heat  is  also  ab- 
sorbed by  the  distilled  water 
which  is  contained  inside  of  the 
telescope.  In  order  to  keep  this 
water  cool,  there  is  an  outside 
jacket  on  the  telescope,  through 
which  circulating  water  may  be 
passed  for  this  purpose.  In  Fig. 
36  is  shown  the  method  of 
arrangement  of  the  telescope 
and  the  arc  lamp;  and  in  Fig. 
32  is  shown  a  set  of  four  of 
these  telescopes  arranged  around 
the  arc  lamp  and  in  actual 
operation.  The  arc  lamp  uses 
from  40  to  80  amperes  and  operates  at  45  to  50  volts. 
'  Blood  is  opaque  to  ultra-violet  light,  and  it  is  therefore  neces- 
sary to  drive  the  blood  away  from  the  diseased  portion  which  is 
to  be  treated.  This  is  accomplished  by  what  is  known  as  a  pres- 
sure glass  shown  in  Fig.  37.  It  consists  of  a  plano-convex  lens  of 
rock  crystal  kept  cool  by  circulating  water— the  glass  acting  to 
focus  the  light  on  the  diseased  portion,  and  also  to  exert  con- 
siderable  pressure  there. 


FIG.   34. — Finsen's    Original 
Blue  Lens  for  Use  with  Sunlight. 


70 


HAMMER:  ULTRA-VIOLET  RAYS. 


The  patient  does  not  suffer  from  exposure  to  the  rays;  but 
after  the  treatment,  which  is  usually  an  hour  and  ten  minutes 
per  day,  he  appears  to  be  considerably  sunburned.  He  is  then 
allowed  to  recuperate  until  the  next  day,  and  the  treatment,  is 
then  repeated.  After  a  series  of  these  treatments,  the  patient 
is  sent  away  apparently  cured.  Sometimes  he  does  not  return; 
but  more  often  he  must  come  back  for  a  second  or  third,  and 
even  more  series  of  treatments,  due  to  the  fact  that  certain  of  the 


1 


FIG.  35. — Finsen  Telescope  Tube,  for  Use  with  Carbon  Arc  Light. 


FIG.  36. — Showing  Arrangement  of  Arc  Lamp  and  Finsen  Tubes. 

microbes  which  have  been  deep-seated-have  worked  their  way  to 
the  surface,  the  disease  having  started  anew. 

It  is  said  that  out  of  over  600  cases  treated  at  Copenhagen, 
there  have  been  only  1  to  2%  of  failures  due  to  fault  in  the  treat- 
ment ;  but  there  have  been  cases  where  the  disease  has  been  in 
such  an  advanced  stage  and  for  such  a  very  long  period  that  it 
has  not  yielded  successfully.  But  I  was  informed  that  in  the 
majority  of  cases  after  very  few  treatments,  the  patients  are  dis- 
missed absolutely  cured.  In  order  that  you  may  properly 


HAMMER:  ULTRA-VIOLET  RAYS. 


71 


FIG.  38. — Showing  Lupus  Vulgaris  Patients  Before  and  After 
Treatment  with  Ultra-Violet  Light  at  the  Finsen  Institute, 
Copenhagen. 


72  HAMMER:  ULTRA-VIOLET  RAYS. 

appreciate  the  remarkable  results  which  have  been  secured  by 
Prof.  Finsen ;  and  the  stupendous  importance  which  his  successful 
combating  of  these  loathsome  forms  of  disease  represents  to 
many  of  he  most  sorely  afflicted  people  of  \his  world,  I  have 
inserted  in  my  paper  several  photographs,  see  Fig.  38,  which  I 
secured  at  the  Finsen  Institute,  of  patients  afflicted  with  lupus 
vulgaris — thess  pictures  showing  them  before  and  after  the 
treatment  with  the  ultra-violet  rays  produced  by  the  arc  light. 
I  feel  that  their  presentation  in  this  paper  requires  no  apology ; 
on  the  contrary,  electrical  engineers  should  feel  a  sense  of  pride 
that  in  the  use  of  the  arc  light  in  this  remarkable  advance  in 
medicine  and  surgery,  their  profession  has  contributed  in  no 
small  degree. 

Those  caring  to  look  up  these  and  similar  cases,  will  find  full 
descriptions  in  English  in  "Phototherapy  after  Finsen's  Meth- 
ods," by  Valdemar  Bie,  M.D.,  Prof.  Finsen's  Assistant  (published 


FIG.  37. — Pressure  Lens. 

by  Lippincott),  or  Die  Bekampfung  des  Lupus  Vulgaris  von  Niels 
R.  Finsen  (Gustav  Fischer,  Jena),  and  Die  Finsen  Therapie  und 
ihr  gegenwiirtigen  Stand  in  der  Dermatologie,  von  Dr.  Forch- 
hammer  (J.  Cohen's  Buchdruckereien,  Kopenhagen). 

The  little  cut  of  Prof.  Finsen  which  heads  this  article  is 
from  an  autograph  portrait  which  Prof.  Finsen  presented  to 
the  writer,  and  it  is  sad  to  contemplate  that  this  man  who  has 
conferred  such  a  priceless  boon  upon  humanity  is  himself  an 
invalid,  suffering  from  an  incurable  disease,  and  one  which  has 
made  it  at  times  well  nigh  impossible  for  him  to  prosecute  his 
work. 

The  Finsen  Institute  was  established  in  1896,  through  the 
munificence  of  Copenhagen's  public-spirited  citizens,  and  through 
a  gift  by  the  city  of  the  property  on  which  it  was  erected. 

The  lecturer  desires  to  express  his  appreciation  of  the  services  rendered 
by  his  assistants,  Messrs.  Varley,  Lawton,  Brown,  Webb,  Scheerer  and 
Dow,  and  also  to  acknowledge  the  courtesies  extended  by  the  New  York 
Edison  Co. 


LIST    OF    WORKS 

ON 

ELECTRICAL  SCIENCE 

PUBLISHED    AND   FOR   SALE   BY 

D.  VAN  NOSTRAND  COMPANY, 

23  Murray  and  27  Warren  Streets,  New  York. 


ABBOTT,   A.    V.     The   Electrical   Transmission   of  Energy.      A  Manual  for  the 
Design  of  Electrical  Circuits.      New  Edition,  revised  and  rewritten.     With 
many  Diagrams  and  Engravings  and  Folding  Plates.     8vo,  cloth.     In  press. 
ANDERSON,  GEO.  L.,  A.M.  (Capt.  U.S.A.).     Handbook  for  the  Use  of  Electricians 
in  the  operation  and  care  of  Electrical  Machinery  and  Apparatus  of  the 
United  States  Seacoast  Defenses.     Prepared  under  the  direction  of  Lieut.- 
GeneraT  Commanding  the  Army.     Illustrated.     8vo,  cloth.     $3.00. 
ARNOLD,   E.      Armature  Windings  of  Direct-Current  Dynamos.     Extension  and 
Application  of  a  general  Winding  Rule.     Translated  from  the  original  German 
by  Francis  B.  DeGress,  M.E.     Illustrated.     8vo,  cloth.     $2.00. 
ATKINSON,  A.  A.,  Prof.  (Ohio  Univ.).     Electrical  and  Magnetic  Calculations.     For 
the  use   of  Electrical  Engineers  and  others  interested  in  the  Theory  and 
Application  of  Electricity  and  Magnetism.     Second  Edition,  revised.      Illus- 
trated.    8vo,  cloth.     Net,  $1.50. 
ATKINSON,     PHILIP.     The    Elements    of    Dynamic    Electricity    and   Magnetism. 

Fourth  Edition.     Illustrated.     8vo,  cloth.     $2.00. 

Elements  of  Electric  Lighting,  including  Electric  Generation,  Measurement, 
Storage,  and  Distribution.  Tenth  Edition,  fully  revised  and  new  matter 
added.  Illustrated.  8vo,  cloth.  $1.50. 

Power  Transmitted  by  Electricity  and  Applied  by  the  Electric  Motor,  including 
Electric  Railway  Construction.     Illustrated.     Fourth  Edition,  fully  revised 
and  new  matter  added.     8vo,  cloth.     $2.00. 
BADT,  F.  B.     New  Dynamo  Tender's  Handbook.     70  Illustrations.     16mo,  cloth. 

$1.00. 
Electric    Transmission    Handbook.      Illustrations   and   Tables.      16mo,    cloth. 

$1.00. 
Incandescent   Wiring   Handbook.     Fourth   Edition.      Illustrations   and   Tables. 

12mo,  cloth.     $1.00. 
Bell-Hanger's  Handbook.     Third  Edition.     Illustrated.     12mo,  cloth.     $1.00- 


2  VAN  NOSTRAND'S  LIST  OF   WORKS 

BIGGS,   C.    H.    W.     First    Principles   of   Electricity   and   Magnetism.     Illustrated. 

12mo,  cloth.     $2.00. 
BLAKESLEY,  T.  H.     Papers  on  Alternating  Currents  of  Electricity.     For  the  u.=e 

of  Students  and  Engineers.     Third  Edition,  enlarged.     12mo,  cloth.     $1.50. 

BOTTONE,  S.  R.  Electrical  Instrument-Making  for  Amateurs.  A  Practical  Hand- 
book. Enlarged  by  a  chapter  on  "The  Telephone."  Sixth  Edition.  With 
43  Illustrations.  12mo,  cloth.  50  cents. 

BOWKER,  WM.  R.  Dynamo,  Motor,  and  Switchboard  Circuits  for  Electrical 
Engineers:  a  practical  book  dealing  with  the  subject  of  Direct,  Alternating, 
and  Polyphase  Currents.  With  over  100  Diagrams  and  Engravings.  8vo, 
cloth.  Illustrated.  Net,  $2.25. 

CLARK,  D.  K.  Tramways:  Their  Construction  and  Working.  Embracing  a 
Comprehensive  History  of  the  System,  with  Accounts  of  the  Various  Modes 
of  Traction,  a  Description  of  the  Varieties  of  Rolling  Stock,  and  Ample  Details 
of  Cost  and  Working  Expenses;  with  Special  Reference  to  the  Tramways  of 
the  United  Kingdom.  Second  Edition,  revised  and  rewritten.  With 
over  400  Illustrations.  Contains  a  section  on  Electric  Traction.  8vo,  cloth. 
$9.00. 

CROCKER,  F.  B.,  and  WHEELER,  S.  S.  The  Practical  Management  of  Dynamos 
and  Motors.  Revised  and  enlarged.  Illustrated.  Sixteenth  Thousand. 
12mo,  cloth.  $1.00. 

CROCKER,  F.  B.  Electric  Lighting.  A  Practical  Exposition  of  the  Art  for  the 
use  of  Electricians,  Students,  and  others  interested  in  the  Installation  or 
Operation  of  Electric-Lighting  Plants.  Volume  I.:  The  Generating  Plant. 
New  Edition,  revised  and  rewritten.  In  press.  Volume  II.:  Distributing 
System  and  Lamps.  Fourth  Edition.  8vo,  cloth.  Each,  $3.00. 

DESMOND,  CHAS.  Electricity  for  Engineers.  Part  I.:  Constant  Current.  Part 
II.:  Alternate  Current.  Revised  Edition.  Illustrated.  12mo,  cloth.  $2.50. 

DYNAMIC  ELECTRICITY;  Its  Modern  Use  and  Measurement,  chiefly  in  its  appli- 
cation to  Electric  Lighting  and  Telegraphy,  including:  1.  Some  Points  in 
Electric  Lighting,  by  Dr.  John  Hopkinson.  2.  On  the  Treatment  of  Electricity 
for  Commercial  Purposes,  by  J.  N.  Shoolbred.  3.  Electric-Light  Arith- 
metic, by  R.  E.  Day,  M.E.  18mo,  boards.  (No.  71  Van  Nostrand's  Science 
Series.)  50  cents. 

EMMETT,  WM.  L.  Alternating-Current  Wiring  and  Distribution.  16mo,  cloth. 
Illustrated.  $1.00. 

EWING,  J.  A.  Magnetic  Induction  in  Iron  and  other  Metals.  Third  Edition,  re- 
viaed.  Illustrated.  8vo,  cloth.  $4.00. 

FI3KE,  BRADLEY  A.,  Lieut.,  U.S.N.  Electricity  in  Theory  and  Practice;  or, 
The  Elements  of  Electrical  Engineering.  Tenth  Edition.  8vo,  cloth.  $2.50. 

FLEMING,  J.  A.,  Prof.     The  Alternate-Current  Transformer  in  Th-ory  and  Prac- 
tice.    Vol.  I.:    The  Induction  of  Electric  Currents.     500  pp.     Fifth  Issue. 
Illustrated.     8vo,    cloth.     $5.00.     Vol.    II.:     The    Utilization    of    Induced 
Currents.     Third  Issue.     594  pp.     Illustrated.     8vo,  cloth.     $5.00. 
Electric  Lamps  and  Electric  Lighting.     Svo,  cloth.     $2.50. 


ON  ELECTRICAL    SCIENCE.  3 

FOSTER,  H.  A.  Electrical  Engineers'  Pocket  Book.  With  the  Collaboration  of 
Eminent  Specialists.  A  handbook  of  useful  data  for  Electricians  and 
Electrical  Engineers.  With  innumerable  Tables,  Diagram,,,  and  Figures 
The  most  complete  book  of  its  kind  ever  published,  treating  of  the  latest 
and  best  Practice  in  Electrical  Engineering.  Third  Edition,  revised.  Pocket 
size,  full  leather,  1000  pp.  $5.00. 

GORDON,  J.  E.  H.     School  Electricity.     12mo,  cloth.     $2.00. 

GORE,  GEORGE,  Dr.  The  Art  of  Electrolytic  Separation  of  Metals  (Theoretical 
and  Practical).  Illustrated.  8vo,  cloth.  $3.50. 

GRAY,  J.  Electrical  Influence  Machines:  Their  Historical  Development  and 
Modern  Forms.  With  Instructions  for  making  them.  Second  Edition, 
revised  and  enlarged.  With  105  Figures  and  Diagrams.  12mo,  cloth.  Illus- 
trated. $2.00. 

GUILLEMIN,  AMEDEE.  Electricity  and  Magnetism.  Translated,  revised,  and 
edited  by  Prof.  Silvanus  P.  Thompson.  600  Illustrations  and  several  Plates. 
Large  8vo,  cloth.  $8.00. 

GUY,  ARTHUR  F.  Electric  Light  and  Power-  Giving  the  result  of  practical  ex- 
perience in  Central-Station  Work.  8vo,  cloth.  Illustrated.  $2.50. 

HAMMER,  W.  J.  Radium,  and  Other  Radio-active  Substances;  Polonium,  Actin- 
ium, and  Thorium.  With  a  consideration  of  Phosphorescent  and  Fluo- 
rescent Substances,  the  properties  and  applications  of  Selenium,  and  the 
treatment  of  disease  by  the  Ultra-Violet  Light.  With  Engravings  and  Plates. 
8vo,  cloth.  Illustrated.  $1.00. 

HASKINS,   C.   H.     The   Galvanometer  and  its   Uses.     A  Manual  for  Electricians 

and  Students.     Fourth  Edition,  revised.     12mo,  morocco.     $1.50. 
Transformers:    Their  Theory,  Construction,  and  Application  Simplified.     Illus- 
trated.    12nu>,  cloth.     $1.25. 

HAWKINS,  C.  C.,  and  WALLIS,  F.  The  Dynamo:  Its  Theory,  Design,  and  Manu- 
facture. 190  Illustrations.  8vo,  cloth.  $3.00. 

HOBBS,  W.  R.  P.  The  Arithmetic  of  Electrical  Measurements.  With  numerous 
examples,  fully  worked.  Ninth  Edition.  12mo,  cloth.  50  cents. 

HOUSTON,  E.  J.,  Prof.  A  Dictionary  of  Electrical  Words,  Terms,  and  Phrases. 
Fourth  Edition,  rewritten  and  greatly  enlarged.  570  Illustrations.  Large 
8vo,  cloth.  $7.00. 

INCANDESCENT  ELECTRIC  LIGHTING.  A  Practical  Description  of  the  Edison 
System,  by  H.  Latimer.  To  which  is  added:  The  Design  and  Operation  of 
Incandescent  Stations,  by  C.  J.  Field;  A  Description  of  the  Edison  Electro- 
lyte Meter,  by  A.  E.  Kennelly;  and  a  Paper  on  the  Maximum  Efficiency  of 
Incandescent  Lamps,  by  T.  W.  Howell.  Illustrated.  16mo,  cloth.  (No. 
57  Van  Nostrand's  Science  Series.)  50  cents. 

INDUCTION  COILS:  Hew  Made  and  How  Used.  Third  Edition.  16mo,  cloth. 
(No.  53  Van  Nostrand's  Science  Series.)  50  cents. 

JEHL,  FRANCIS,  Member  A.I.E.E.  The  Manufacture  of  Carbons  for  Electric 
Lighting  and  other  purposes.  Illustrated  with  numerous  Diagrams,  Tables, 
and  Folding  Plates.  Illustrated.  Cvo,  cloth.  $4.00. 


4  VAN  NOSTRAND'S  LIST  OF   WORKS 

KAPP,  GISBERT,  C.E.  Electric  Transmission  of  Energy  and  its  Transformation, 
Subdivision,  and  Distribution.  A  Practical  Handbook.  Fourth  Edition, 
thoroughly  revised.  12mo,  cloth.  $3.50. 

Alternate-Current  Machinery.  190  pp.  Illustrated.  (No.  96  Van  Nostrand's 
Science  Series.)  50  cents. 

Dynamos,  Alternators,  and  Transformers.     Illustrated.     8vo,  cloth.     $4.00. 

KELSEY,  W.  R.  Continuous-Current  Dynamos  and  Motors,  and  their  Control; 
being  a  series  of  articles  reprinted  from  the  "Practical  Engineer,"  and  com- 
pleted by  W.  R.  Kelsey,  B.Sc.  With  Tables,  Figures,  and  Diagrams.  8vo, 
cloth.  Illustrated.  $2.50. 

KEMPE,  H.  R.     The  Electrical  Engineer's  Pocket-Book:    Modern  Rules,  Formulae, 
Tables,  and  Data.     Second  Edition,  with  additions.     32mo,  leather.     $1.75. 
A   Handbook   of  Electrical    Testing.     Fifth   Edition.     200    Illustrations.     8vo, 
cloth.     $6.00. 

KENNELLY,  A.  E.  Theoretical  Elements  of  Electro-Dynamic  Machinery.  Vol.  I. 
Illustrated.  8vo,  cloth.  $1.50. 

KILGOUR,  M.  H.,  SWAN,  H.,  and  BIGGS,  C.  H.  W.  Electrical  Distribution:  Its 
Theory  and  Practice.  Illustrated.  8vo,  cloth.  $4.00. 

LIVERMORE,  V.  P.,  and  WILLIAMS,  J.  How  to  Become  a  Competent  Motorman: 
being  a  practical  treatise  on  the  proper  method  of  operating  a  street-railway 
motor-car;  also  giving  details  how  to  overcome  certain  defects.  16mo, 
cloth.  Illustrated.  $1.00. 

LOCKWOOD,  T.  D.  Electricity,  Magnetism,  and  Electro- Telegraphy.  A  Prac- 
tical Guide  and  Handbook  of  General  Information  for  Electrical  Students, 
Operators,  and  Inspectors.  Fourth  Edition.  Illustrated.  8vo,  cloth. 
$2.50. 

LORING,  A.  E.  A  Handbook  of  the  Electro-Magnetic  Telegraph.  Fourth  Edition, 
revised.  16mo,  cloth.  (No.  39  Van  Nostrand's  Science  Series.)  50  cents. 

MANSFIELD,  A.  N.  Electromagnets:  Their  Design  and  Construction.  (Van 
Xostrand's  Science  Series,  No.  C4.)  50  cents. 

MARTIN,  T.  C.,  and  WETZLER,  J.  The  Electro-Motor  and  its  Applications. 
Fourth  Edition,  with  an  Appendix  on  the  Development  of  the  Electric 
Motor  since  1888,  by  Dr.  L.  Bell.  300  Illustrations.  4to,  cloth.  $3.00. 

MAVER,  WM.,  Jr.  American  Telegraphy  and  Encyclopedia  of  the  Telegraph  Sys- 
tems, Apparatus,  Operations.  430  Illustrations.  Fifth  Edition,  revised. 
8vo,  cloth.  $3.50 

NIPHER,  FRANCIS  E.,  A.M.  Theory  of  Magnetic  Measurements.  With  an 
Appendix  on  the  Method  of  Least  Squares.  12mo,  cloth.  $1.00. 

NOLL,  AUGUSTUS.  How  to  Wire  Buildings.  A  Manual  of  the  Art  of  Interior 
Wiring.  Fourth  Edition.  8vo,  cloth.  Illustrated.  $1.50. 

OHM,  G.  S.,  Dr.  The  Galvanic  Circuit  Investigated  Mathematically.  Berlin, 
1827.  Translated  by  William  Francis.  With  Preface  and  Notes  by  the 
Editor,  Thos.  D.  Lock  wood.  12mo,  cloth.  (No.  102  Van  Nostrand's 
Science  Series.)  50  cents. 


ON  ELECTRICAL   SCIENCE.  5 

OUDIN,  MAURICE  A.  M.  S.  Standard  Polyphase  Apparatus  and  Systems.  Illus- 
trated with  many  Photo-Reproductions,  Diagrams,  and  Tables.  Third  Edi- 
tion, revised.  8vo,  cloth.  $3.00. 

PALAZ,  A.  Treatise  on  Industrial  Photometry.  Specially  applied  to  Electric 
Lighting.  Translated  from  the  French  by  G.  W.  Patterson,  Jr.,  Assistant 
Professor  of  Physics  in  the  University  of  Michigan,  and  M.  R.  Patterson,  B.A. 
Second  Edition.  Fully  Illustrated.  8vo,  cloTh.  $4.00. 

PARR,  G.  D.  A.  Electrical  Engineering  Measuring  Instruments,  for  Commercial 
and  Laboratory  Purposes.  With  370  Diagrams  and  Engravings.  8vo,  cloth. 
Illustrated.  Net,  $3.50. 

PARSHALL,  H.  F.,  and  HOBART,  H.  M.  Armature  Windings  of  Electric  Machines. 
With  140  full-page  Plates,  65  Tables,  and  descriptive  letter-press.  4to, 
cloth.  $7.50. 

PERRINE,  F.  A.  C.,  A.M.,  D.Sc.  Conductors  for  Electrical  Distribution:  Their 
Manufacture  and  Materials,  the  Calculation  of  Circuits,  Pole-Line  Construc- 
tion, Underground  Working,  and  other  Uses.  8vo,  cloth.  Illustrated.  $3.50. 

.PERRY,  NELSON  W.  Electric  Railway  Motors:  Their  Construction,  Operation, 
and  Maintenance.  An  Elementary  Practical  Handbook  for  those  engaged  in 
the  management  and  operation  of  Electric  Railway  Apparatus,  with  Rules 
and  Instructions  for  Motormen.  12mo,  cloth.  $1.00. 

PLANTE,  GASTON.  The  Storage  of  Electrical  Energy,  and  Researches  in  the 
Effects  created  by  Currents  combining  Quantity  witli  High  Tension.  Trans- 
lated from  the  French  by  Paul  B.  Elwell.  89  Illustrations.  8vo.  $4.00. 

POPE,  F.  L.  Modern  Practice  of  the  Electric  Telegraph.  A  Handbook  for  Elec- 
tricians and  Operators.  An  entirely  new  work,  revised  and  enlarged,  and 
brought  up  to  date  throughout.  Illustrations.  8vo,  cloth.  $1.50. 

RAYMOND,  E.  B.  Alternating-Current  Engineering,  Practically  Treated.  With 
many  Figures  and  Diagrams.  In  press. 

SALOMONS,  Sir  DAVID,  M.A.  Electric-Light  Installations.  A  Practical  Hand- 
book. Seventh  Edition,  revised  and  enlarged.  Vol.  L:  Management  of 
Accumulators.  Illustrated.  12mo,  cloth.  $1.50.  Vol.  II.:  Apparatus. 
Illustrated  12mo,  cloth.  $2.25.  Vol.  III.:  Application.  Illustrated. 
12mo,  cloth.  $1.50. 

SCHELLEN,  H.,  Dr.  Magneto-Electric  and  Dynamo-Electric  Machines.  Their 
Construction  and  Practical  Application  to  Electric  Lighting  and  the  Trans- 
mission of  Power.  Translated  from  the  Third  German  Edition  by  N.  S.  Keith 
and  Percy  Neymann,  Ph.D.  With  very  large  Additions  and  Notes  relating 
to  American  Machines,  by  N.  S.  Keith.  Vol.  I.  With  353  Illustrations. 
Third  Edition.  $5.00. 

SEVER,  G.  F.  Electrical  Engineering  Experiments  and  Tests  on  Direct-Current 
Machinery.  With  Diagrams  and  Figure;.  8vo,  pamphlet.  Illustrated. 
$1.00. 

SEVER,  G.  F.,  and  TOWNSEND,  F.  Laboratory  and  Factory  Tests  in  Electrical 
Engineering.  8vo,  cloth.  Illustrated.  In  press. 


6  VAN  NOSTRAND'S   LIST   OF    WORKS 

SEWALL,  C.  H.  Wireless  Telegraphy.  With  Diagrams  and  Figures.  Second 
Edition,  corrected.  8vo,  cloth.  Illustrated.  $2.00. 

SHELDON,  SM  Ph.D.,  and  MASON,  H.,  B.S.  Dynamo- Electric  Machinery:  Its 
Construction,  Design,  and  Operation.  Direct-Current  Machines.  Fourth 
Edition,  revised.  Illustrated.  8vo,  cloth.  Net,  $2.50. 

Alternating-Current  Machines;  being  the  second  volume  of  the  authors'  "Dy- 
namo-Electric Machinery:  its  Construction,  Design,  and  Operation."  With 
many  Diagrams  and  Figures.  (Binding  uniform  with  Volume  I.)  Third 
Edition.  Illustrated.  8vo,  cloth.  Net,  $2.50. 

SLOANE,  T.  O'CONOR,  Prof.  Standard  Electrical  Dictionary.  300  Illustrations. 
8vo,  cloth.  $3.00. 

SNELL,  ALBION  T.  Electric  Motive  Power.  The  Transmission  and  Distribution 
of  Electric  Power  by  Continuous  and  Alternate  Currents.  With  a  Section 
on  the  Applications  of  Electricity  to  Mining  Work.  Illustrated.  8vo,  cloth. 
$4.00. 

SODDY,  F.  Radio-activity:  An  Elementary  Treatise  from  the  Standpoint  of  the 
Disintegration  Theory.  Fully  Illustrated,  and  with  a  complete  table  of 
Contents  and  Extended  Index.  8vo,  cloth.  In  press. 

SWINBURNE,  JAS.,  and  WORDINGHAM,  C.  H.  The  Measurement  of  Electric 
Currents.  Electrical  Measuring  Instruments.  Meters  for  Electrical  Energy. 
Edited,  with  Preface,  by  T.  Commerford  Martin.  Folding  Plate  and  numer- 
ous Illustrations.  16mo,  cloth.  59  cents. 

SWOOPE,  C.  WALTON.  Practical  Lessons  in  Electricity:  Principles,  Experi- 
ments, and  Arithmetical  Problems.  An  Elementary  Text-book.  With 
numerous  Tables,  Formula-,  and  two  large  Instruction  Plates.  Fifth  Edition. 
Illustrated.  8vo,  cloth.  Net,  $2.00. 

THOM,  C.,  and  JONES,  W.  H.  Telegraphic  Connections,  embracing  recent  methods 
in  Quadruplex  Telegraphy.  20  Colored  Plates.  8vo,  cloth.  $1.50. 

THOMPSON,  S.  P.,  Prof.  Dynamo-Electric  Machinery.  With  an  Introduction 
and  Notes  by  Frank  L.  Pope  and  H.  R.  Butler.  Fully  Illustrated.  (No.  66 
Van  Nostrand's  Science  Series.)  50  cents. 

Recent  Progress  in  Dynamo-Electric  Machines.  Being  a  Supplement  to 
"Dynamo-Electric  Machinery."  Illustrated.  12mo,  cloth.  (No.  75  Van 
Nostrand's  Science  Series.)  50  cents. 

TREVERT,  E.  How  to  Build  Dynamo-Electric  Machinery.  Embracing  the 
Th'eory,  Designing,  and  Construction  of  Dynamos  and  Motors.  With 
Appendices  on  Field-Magnet  and  Armature  Winding,  Management  of 
Dynamos  and  Motors,  and  useful  Tables  of  Wire  Gauges.  Illustrated. 
8vo,  cloth.  $2.50. 

TUNZELMANN,  G.  W.  de.  Electricity  in  Modem  Life.  Illustrated.  12mo, 
cloth.  $1.25. 

UNDERBILL,  C.  R.  The  Electromagnet:  Being  a  new  and  revised  edition  of 
"The  Electromagnet,"  by  Townsend  Walcott,  A.  E.  Kennelly,  and  Richard 
Varley.  With  Tables  and  Numerous  Figures  and  Diagrams.  12mo,  cloth. 
Illustrated.  $1.50. 


ON  ELECTRICAL    SCIENCE.  7 

URQUHART,  J.  W.  Dynamo  Construction.  A  Practical  Handbook  for  the  use 
of  Engineer  Constructors  and  Electricians  in  Charge.  Illustrated  l^mo 
cloth.  $3.00. 

Electric  Ship-Lighting.  A  Handbook  on  the  Practical  Fitting  and  Running  of 
Ships'  Electrical  Plant,  for  the  ur,e  of  Ship  Owners  and  Builders,  Marine 
Electricians,  and  Sea-going  Engineers  in  Charge.  88  Illustrations.  12mo, 
cloth.  $3.00. 

Electric-Light  Fitting.  A  Handbook  for  Working  Electrical  Engineers,  cm- 
bodying  Practical  Notes  on  Installation  Management.  Second  Edition,  with 
additional  chapters.  With  numerous  Illustrations.  12mo,  cloth.  $2.09. 

WADE,  E.  J.  Secondary  Batteries:  Their  Theory,  Construction,  and  Use.  With 
innumerable  Diagrams  and  Figures.  8vo,  cloth.  Illustrated.  Net,  $4.00. 

WALKER,  FREDERICK.  Practical  Dynamo-Building  for  Amateurs.  How  to 
Wind  for  any  Output.  Illustrated.  16mo,  cloth.  (No.  98  Van  Nostrand's 
Science  Series.)  50  cents. 

WALLING,  B.  T.,  Lieut.-Com.  U.S.N.,  and  MARTIN,  JULIUS.  Electrical  Installa- 
tions of  the  United  States  Navy.  With  many  Diagrams  and  Engravings. 
In  press. 

WALMSLEY,  R.  M.  The  Electric  Current.  How  Produced  and  How  Used.  With 
379  Illustrations.  12mo,  cloth.  $2.50. 

WEBB,  H.  L.  A  Practical  Guide  to  the  Testing  of  Insulated  Wires  and  Cables. 
Illustrated.  12mo,  cloth.  $1.00. 

WEYMOUTH,  F.  MARTEN.  Drum  Armatures  and  Commutators.  (Theory  and 
Practice.)  A  complete  treatise  on  the  theory  and  construction  of  drum- 
winding,  and  of  commutators  for  closed-coil  armatures,  together  with  a  full 
resume  of  some  of  the  principal  points  involved  in  their  design;  and  an 
exposition  of  armature  reactions  and  sparking.  Illustrated.  Svo,  cloth. 
$3.00. 

WORMELL,  R.  Electricity  in  the  Service  of  Man.  A  Popular  and  Practical 
Treatise  on  the  Application  of  Electricity  in  Modern  Life.  From  the  Ger- 
man, and  edited,  with  copious  additions,  by  R.  Wormell,  and  an  Introduc- 
tion by  Prof.  J.  Perry.  With  nearly  850  Illustrations.  Svo,  cloth.  $5.00. 


THIRD  EDITION,  REVI5EP. 

Pocket  Size,  Flexible  Leather,  1,OOO  Pages,  with  innumerable  Piagran 
Illustrations  and  Tables.    PRICE,  $5.OO. 

[LEGTRICAL  [NGINEER'S  POCKETBOO 

The  Most  Complete  Book  of  its  kind  ever  Published,  Treating 
of  the  Latest  and  Best  Practice  in  Electrical  Engineering, 

By  HORATIO  A.  FOSTER, 

Member  Amer.  Inst.  E.  £.,  Member  Amer.  Soc.  M,  E. 

_(WITH   THE   COLLABORATION    OF    EMINENT   SPECIALISTS.] 

CONTENTS. 

Electrical  Engineering  Syi 
bols.  Electrical  Engineer!] 
Units.  Description  of  Instr 
ments.  Resistance  Measui 
ment.  Measurement  of  E.M. 
Measurement  of  Capaci 
Measurement  of  Inductanc 
Measurement  of  Power  on  J 
ternating  Current  Circuit 
Tests  with  Yoltmeter.  Dete 
mination  of  Magnetic  Propfi 
ties  of  Iron  and  Steel.  Dete 
mination  of  Wave  Form  of  i 
M.  F.  and  Current.  Condu< 
ors,  Properties  of. '  Conduc 
or-.  Relation  and  Dimensioi 
of,  for  Transmission  of  Ele 
trie  Current.  Transmission] 
Power.  Switchboards  ai 
Switching  Devices.  Cable  Tei 
ing.  Electromagnets.  Dyn 
mos.  Motors.  Testing  Dyn 
mos  and  Motors.  Static  Tran 
formers.  Electric  Lightioj 
Electric  Railways.  Storai 
Batteries.  Telegraph.  Tel 
phone.  Electro-Chemistr; 
Electro-Metallurgy.  Electr 
Heating,  Welding  and  Cool 
ing.  Electricity  Meters.  Ligh 
ning  Arresters.  Lightnin 
Conductors.  National  Cod 
Rules  and  Requirements.  Mi 
cellaneous  Electrical  Dati 
Certain  Uses  of  Electricity  I 
factual  size.  U.S.  Army  and  Navy.  Mechai 

ical  Section.    Index. 

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LESSONS  IN 

RAcriCAL  ELECTRICITY 

PRINCIPLES,  EXPERIMENTS,  AND  ARITHMETICAL  PROBLEMS. 
AN     ELEMENTARY    TEXT    BOOK 

\th    Numerous    Tables,    Formulae,    and    Two    Large    Instruction    Plates. 

BY 

C.  WALTON   SWOOPE 

Associate  Member  American  Institute  of  Electrical  Engineers, 

Instructor  of  Applied  Electricity  at  the  Spring 

Garden  Institute,  Philadelphia. 


Five  years  ago  the  author  prepared  a  private  edition  of  "  Lessons  in  Practical  Electricity,"  which 

published  by  the  Spring  Garden  Institute  for  the  use  of  its  evening  classes  in  practical  electricity. 

The  demand  for  the  book  arose  from  two  facts  :  First — these  classes,  being  composed  of  young 
i  engaged  in  various  occupations  who  desired  to  obtain  a  beginner's  knowledge  of  the  principles  and 
hmetic  of  applied  electricity,  were  very  large  ;  Second — an  unsuccessful  attempt  was  made  to  obtain 
>ok  suitable  for  thoroughly  supplementing  a  combined  course  of  lectures  and  individual  laboratory 
k. 

The  educational  success  attained  at  the  Institute,  and  also  at  several  other  schools  which  secured 
privilege  of  obtaining  copies  of  the  edition  (now  exhausted),  and  the  fact  that  the  former  situation 

again  to  be  met,  seemed  to  warrant  the  preparation  of  the  present  volume,  which  has  been  entirely 
pritten  and  several  hundred  new  illustrations  introduced. 

An  attempt  has  been  made  to  combine  in  this  book  :  (1)  the  principles  of  electricity  upon  which 
practical  applications  of  to-day  depend  ;  (2)  the  experimental  demonstration  of  these  principles  ; 
the  elements  of  the  arithmetic  of  electricity  used  in  making  practical  electrical  measurements  and 
jilations. 

Illustrations  have  been  generously  introduced  to  make  the  principles  clear,  in  preference  to  pictures 
lectrical  machinery  in  common  use,  these  being  supplemented  by  numbered  experiments,  which  may 
:onducted  with  simple  and  inexpensive,  yet  efficient,  apparatus  such  as  that  described,  which  was 
gned  for,  and  is  now  used  by  the  Institute. 

A  knowledge  of  fractions,  decimals  and  simple  proportion  will  enable  the  student  to  make  nearly 
;he  calculations. — Preface. 

CONTENTS. 

sson  I.— Magnetism.  II.— Magnetisation.  III.— Magnetic  Fields.  IV.— Theory  of 
Magnetism.  V.-Magnetic  Induction.  VI.-Magnetic  Circuits.  VII.-Earth's  Mag- 
netism. VIII.— Voltaic  Electricity.  IX. -Batteries.  X. -Electrolysis.  XI. -Meas- 
urement of  Current  Strength.  XII. -Resistance.  XlU.-Ohm's  Law  and  Battery 
Connections.  XIV.— Circuits  and  Their  Resistance.  XV.-Electromagnetism. 
XVI.-Galvanometers.  XVII. -Electromagnets.  XVMh— Ammeters.  XIX. -Elec- 
trical Work  and  Power.  XX.  Measurement  of  Pressure.  XXJ. -Measurement 
of  Resistance.  XXII. -Electrical  Development'of  Heat.  XXIII. -Electrodynam- 
ics. XXIV. -Electromagnetic  Induction.  XXV. -The  Induction  Coil.  XXVI. 
Dynamo-Electric  Machines.  XXVI  I. -Armatures.  XXVIII. -Direct  Current 
Dynamos.  XXIX. -Direct  Current  Motors.  XXX. -Electric  Lighting.  Appen- 
dix. Index. 

D.  VAN  NOSTRAND  COHPANY. 

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12mo.    Cloth,  Illustrated,  127  pp.      -     -      Price,    $1.00 

How  and  WH> 
of  Electricity 

BY 

CHARLES    TRIPLER    CHILD, 

Late  Technical  Editor  of  the  "Electrical  Review" 


CONTENTS. 

Preface.  The  Electric  Current,  The  Electric  Battery. 
The  Effects  of  Electric  Flow  in  the  Circuit — Heat  and  Chemi- 
cal Action.  The  Effects  of  Electric  Flow  Outside  the  Circuit — 
Magnetism  and  Induction — The  Electrical  Units.  Electromag- 
nets— The  Telegraph.  Electric  Signaling  Apparatus.  The 
Relations  Between  Magnets  and  Electric  Currents.  Induction 
and  Reactive  Coils.  The  Telephone.  Telephone  Accessories. 
The  Mechanical  Generation  of  Electricity.  The  Dynamo 
Machine.  Various  Types  of  Dyitamo  Machines.  Alternators 
— Polyphase  Currents.  The  Electric  Motor.  The  Electric 
Railway.  Polyphase  Currents  and  Motors.  Electrical  Power 
Transmission.  The  Incandescent  Light.  The  Arc  Light. 
Electrochemistry — Storage  Batteries.  Wireless  Telegraphy. 
Radiation — X-Rays. 


"Is  admirably  adapted  to  instruct  the  non-technical  reader  -who  is  interested  in  that  subje 
*  *  *  Mr.  Child  enjoyed  a  high  reputation  for  the  clearness  and  intelligibility  of  his  wri 
ing,  and  the  volume  in  question  exhibits  these  qualities.  " — New  York  Tribune.  December  2 
1902. 

"In  spite  of  the  great  mass  of  electrical  literature  already  existing,  it  is  one  of  the  first  got 
books  of  its  kind.  *  *  *  It  will  find  a  large  circle  of  readers  on  its  evident  merits. "- 
Engineering  News,  New  York,  February  19,  1903. 

"  Mr.  Child  has  left  a  good  book  ;  one  that  we  cm  heartily  commend  to  the  non-technic 
readers  for  whom  it  was  written  ;  they  will  not  be  led  astray  by  platitudinous  nonsense,  bi 
will  receive  solid,  exact  information  if  simply  expressed."—  Western  Electrician  Chicac 
February  21,  1903. 


D.  VAN  NOSTRAND  COflPANY, 

Publishers   and    Booksellers, 

23    HURRAY    AND    27    WARREN    STREETS,    NEW    YORK. 

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JUST   ISSUED. 

o.  Cloth,  Illustrated,  20O  Pages,      -      .       Price,  S4.OO  Net. 

'RACTIGALX  RAY  WORK 

WITH  TWELVE  PLATES  FROM  PHOTOGRAPHS  OF  X  RAY  WORK, 

— BY — 

FRANK  T.  ADDYMAN, 

B.Se.  (Lond.),  F.I.C. 


CONTENTS. 
PART  I.— HISTORICAL. 

JCHAP.  I.  Introduction.  CHAP.  II.  Work  Leading  Up  to  the  Discovery  of  the 
,ays.  CHAP.  III.  The  Discovery. 

FART  II.— APPARATUS  AND  ITS  MANAGEMENT. 

CHAP.  I.  Electrical  Terms.  CHAP.  II.  Sources  of  Electricity.  CHAP.  III. 
Iction  Coils.  CHAP.  IV.  Electro-static  Machines.  CHAP.  V.  Tubes.  CHAP. 
[Air  Pumps.  CHAP.  VII.  Tube-holders  and  Stereoscopic  Apparatus.  CHAP. 
[.  Fluorescent  Screens. 

PART  III.— PRACTICAL    X    RAY    WORK. 

CHAP.  I.  Installations.  CHAP.  II.  Radioscopy.  CHAP.  III.  Radiography. 
p.  IV.  X  Rays  in  Dentistry.  CHAP.  V.  X  Rays  in  Chemistry.  CHAP.  VI. 

Sys  in  War.     Index.  

LIST  OF  PLATES. 

FRONTISPIECE — Congenital  Dislocation  of  Hip-joint.  I.  Needle  in  Finger. 
Needle  in  Foot.  III.  Revolver  Bullet  in  Calf  and  Leg.  IV.  A  Method  of 
ilization.  V.  Stellate  Fracture  of  Patella  showing  Shadow  of  "Strapping." 
Sarcoma.  VII.  Six-weeks'-old  Injury  to  Elbow  showing  New  Growth  of 
p.  VIII.  Old  Fracture  of  Tibia  and  Fibula  Badly  Set.  IX.  Heart  Shadow. 
Fractured  Femur  showing  Grain  of  Splint.  XI.  Barrell's  Method  of  Localize 

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